Intel 8085
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The Intel 8085 ("''eighty-eighty-five''") is an
8-bit In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data bu ...
microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...
produced by
Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...
and introduced in March 1976. It is software-
binary compatible Binary-code compatibility (binary compatible or object-code compatible) is a property of a computer system, meaning that it can run the same executable code, typically machine code for a general-purpose computer central processing unit (CPU), ...
with the more-famous
Intel 8080 The Intel 8080 is Intel's second 8-bit computing, 8-bit microprocessor. Introduced in April 1974, the 8080 was an enhanced successor to the earlier Intel 8008 microprocessor, although without binary compatibility.'' Electronic News'' was a week ...
. It is the last 8-bit microprocessor developed by Intel. The "5" in the part number highlighted the fact that the 8085 uses a single +5-
volt The volt (symbol: V) is the unit of electric potential, Voltage#Galvani potential vs. electrochemical potential, electric potential difference (voltage), and electromotive force in the International System of Units, International System of Uni ...
(V) power supply, compared to the 8080's +5, -5 and +12V, which makes the 8085 easier to integrate into systems that by this time were mostly +5V. The other major change was the addition of a
serial port A serial port is a serial communication Interface (computing), interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in Pa ...
, with separate input and output pins. This was often all that was needed in simple systems and eliminated the need for separate
integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...
s to provide this functionality, as well as simplifying the
computer bus In computer architecture, a bus (historically also called a data highway or databus) is a communication system that transfers data between components inside a computer or between computers. It encompasses both hardware (e.g., wires, optical ...
as a result. The only changes in the
instruction set In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, s ...
compared to the 8080 were instructions for reading and writing data using these pins. The 8085 is supplied in a 40-pin DIP package. Given the new serial pins, this required
multiplexing In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource†...
8-bits of the address (AD0-AD7) bus with the data bus. This means that specifying a complete 16-bit address requires it to be sent as two 8-bit values, and one of those two has to be temporarily stored, or latched, using separate hardware. Intel manufactured several support chips with an address latch built in. These include the 8755, with an address latch, 2 KB of
EPROM An EPROM (rarely EROM), or erasable programmable read-only memory, is a type of programmable read-only memory (PROM) integrated circuit, chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored d ...
and 16 I/O pins, and the 8155 with 256 bytes of RAM, 22 I/O pins and a 14-bit programmable timer/counter. The multiplexed address/data bus reduced the number of PCB tracks between the 8085 and such memory and I/O chips. While the 8085 was an improvement on the 8080, it was eclipsed by the
Zilog Z80 The Zilog Z80 is an 8-bit computing, 8-bit microprocessor designed by Zilog that played an important role in the evolution of early personal computing. Launched in 1976, it was designed to be Backward compatibility, software-compatible with the ...
in the early-to-mid-1980s, which took over much of the desktop computer role. Although not widely used in computers, the 8085 had a long life as a microcontroller. Once designed into such products as the DECtape II controller and the VT102 video terminal in the late 1970s, the 8085 served for new production throughout the lifetime of those products.


Description

The 8085 is a conventional von Neumann design based on the Intel 8080. Unlike the 8080 it does not multiplex state signals onto the data bus, but the 8-bit data bus is instead multiplexed with the lower eight bits of the 16-bit
address bus In computer architecture, a bus (historically also called a data highway or databus) is a communication system that transfers data between components inside a computer or between computers. It encompasses both hardware (e.g., wires, optical ...
to limit the number of pins to 40. State signals are provided by dedicated bus control signal pins and two dedicated bus state ID pins named S0 and S1. Pin 40 is used for the power supply (+5 V) and pin 20 for ground. Pin 39 is used as the Hold pin. The Intel 8085 processor was designed using nMOS circuitry, with later "H" versions implemented in Intel's enhanced nMOS process known as HMOS II ("High-performance MOS"), which was originally developed for fast static RAM products.Intel Corporation, "New Products: HMOS MCS-85 Chips Uses 20 to 30 Percent Less Power", Solutions, July/August 1981, Page 22 Unlike the 8080, the 8085 requires only a single 5-volt power supply, similar to its competing processors. The 8085 contains approximately 6,500
transistor A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...
s. The 8085 incorporates the functions of the 8224 (clock generator) and the 8228 (system controller) on chip, increasing the level of integration. A downside compared to similar contemporary designs (such as the Z80) is the fact that the buses require demultiplexing; however, address latches in the Intel 8155, 8355, and 8755 memory chips allow a direct interface, so an 8085 along with these chips is almost a complete system. The 8085 has extensions to support new
interrupt In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted ...
s, with three maskable vectored interrupts (RST 7.5, RST 6.5 and RST 5.5), one
non-maskable interrupt In computing, a non-maskable interrupt (NMI) is a hardware interrupt that standard interrupt-masking techniques in the system cannot ignore. It typically occurs to signal attention for non-recoverable hardware errors. Some NMIs may be masked, but ...
(TRAP), and one externally serviced interrupt (INTR). Each of these five interrupts has a separate pin on the processor, a feature which permits simple systems to avoid the cost of a separate interrupt controller. The RST 7.5 interrupt is edge triggered (latched), while RST 5.5 and 6.5 are level-sensitive. All interrupts except TRAP are enabled by the EI instruction and disabled by the DI instruction. In addition, the SIM (Set Interrupt Mask) and RIM (Read Interrupt Mask) instructions, the only instructions of the 8085 that are not from the 8080 design, allow each of the three maskable RST interrupts to be individually masked. All three are masked after a normal CPU reset. SIM and RIM also allow the global interrupt mask state and the three independent RST interrupt mask states to be read, the pending-interrupt states of those same three interrupts to be read, the RST 7.5 trigger-latch flip-flop to be reset (cancelling the pending interrupt without servicing it), and serial data to be sent and received via the SOD and SID pins, respectively, all under program control and independently of each other. SIM and RIM each execute in four clock cycles (T states), making it possible to sample SID and/or toggle SOD considerably faster than it is possible to toggle or sample a signal via any I/O or memory-mapped port, e.g. one of the port of an 8155. (In this way, SID can be compared to the SO Set Overflow"pin of the 6502 CPU contemporary to the 8085.) Like the 8080, the 8085 can accommodate slower memories through externally generated
wait state A wait state is a delay experienced by a computer processor when accessing external memory or another device that is slow to respond. Computer microprocessors generally run much faster than the computer's other subsystems, which hold the data the ...
s (pin 35, READY), and has provisions for
Direct Memory Access Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system computer memory, memory independently of the central processing unit (CPU). Without DMA, when the CPU is using programmed i ...
(DMA) using HOLD and HLDA signals (pins 39 and 38). An improvement over the 8080 is that the 8085 can itself drive a piezoelectric crystal directly connected to it, and a built-in clock generator generates the internal high-amplitude two-phase clock signals at half the crystal frequency (a 6.14 MHz crystal would yield a 3.07 MHz clock, for instance). The internal clock is available on an output pin, to drive peripheral devices or other CPUs in lock-step synchrony with the CPU from which the signal is output. The 8085 can also be clocked by an external
oscillator Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...
(making it feasible to use the 8085 in synchronous multi-processor systems using a system-wide common clock for all CPUs, or to synchronize the CPU to an external time reference such as that from a video source or a high-precision time reference). The 8085 is a
binary compatible Binary-code compatibility (binary compatible or object-code compatible) is a property of a computer system, meaning that it can run the same executable code, typically machine code for a general-purpose computer central processing unit (CPU), ...
follow-up on the 8080. It supports the complete
instruction set In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, s ...
of the 8080, with exactly the same instruction behavior, including all effects on the CPU flags (except for the AND/ANI operation, which sets the AC flag differently). This means that the vast majority of object code (any program image in ROM or RAM) that runs successfully on the 8080 can run directly on the 8085 without translation or modification. (Exceptions include timing-critical code and code that is sensitive to the aforementioned difference in the AC flag setting or differences in undocumented CPU behavior.) 8085 instruction timings differ slightly from the 8080—some 8-bit operations, including INR, DCR, and the heavily used MOV r,r instructions, are one clock cycle faster, but instructions that involve 16-bit operations, including stack PUSH (which decrements the 16-bit SP register) generally one cycle slower. Conditional jumps not taken are three clocks faster on the 8085. As mentioned already, only the SIM and RIM instructions were new to the 8085.Note that the Z80 assigns different instructions—two of the Z80's 6 relative jumps—to the opcodes that the 8085 uses for RIM and SIM, making 8085 programs that use these instructions generally unable to run on the Z80 without modification. Since use of these instructions usually relates to 8085-specific hardware features, the necessary program modification would typically be nontrivial.


Programming model

The processor has seven 8-bit registers accessible to the programmer, named A, B, C, D, E, H, and L, where A is also known as the accumulator. The other six registers can be used as independent byte-registers or as three 16-bit register pairs, BC, DE, and HL (or B, D, H, as referred to in Intel documents), depending on the particular instruction. Some instructions use HL as a (limited) 16-bit accumulator. As in the 8080, the contents of the memory address pointed to by HL can be accessed as pseudo register M. It also has a 16-bit
program counter The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 and Itanium microprocessors, and sometimes called the instruction address register (IAR), the instruction counter, or just part of the instruction sequencer, ...
and a 16-bit stack pointer to memory (replacing the 8008's internal
stack Stack may refer to: Places * Stack Island, an island game reserve in Bass Strait, south-eastern Australia, in Tasmania’s Hunter Island Group * Blue Stack Mountains, in Co. Donegal, Ireland People * Stack (surname) (including a list of people ...
). Instructions such as PUSH PSW, POP PSW affect the Program Status Word (accumulator and flags). The accumulator stores the results of arithmetic and logical operations, and the flags register bits (sign, zero, auxiliary carry, parity, and carry flags) are set or cleared according to the results of these operations. The sign flag is set if the result has a negative sign (i.e. it is set if bit 7 of the accumulator is set). The auxiliary or half carry flag is set if a carryover from bit 3 to bit 4 occurred. The parity flag is set to 1 if the parity (number of 1-bits) of the accumulator is even; if odd, it is cleared. The zero flag is set if the result of the operation was 0. Lastly, the carry flag is set if a carryover from bit 7 of the accumulator (the MSB) occurred.


Commands/instructions

As in many other 8-bit processors, all instructions are encoded in a single byte (including register-numbers, but excluding immediate data), for simplicity. Some of them are followed by one or two bytes of data, which can be an immediate operand, a memory address, or a port number. A NOP "no operation" instruction exists, but does not modify any of the registers or flags. Like larger processors, it has CALL and RET instructions for multi-level procedure calls and returns (which can be conditionally executed, like jumps) and instructions to save and restore any 16-bit register-pair on the machine stack. There are also eight one-byte call instructions (RST) for subroutines located at the fixed addresses 00h, 08h, 10h,...,38h. These are intended to be supplied by external hardware in order to invoke a corresponding interrupt-service routine, but are also often employed as fast system calls. One sophisticated instruction is XTHL, which is used for exchanging the register pair HL with the value stored at the address indicated by the stack pointer.


8-bit instructions

All two-operand 8-bit arithmetic and logical (ALU) operations work on the 8-bit accumulator (the A register). For two-operand 8-bit operations, the other operand can be either an immediate value, another 8-bit register, or a memory cell addressed by the 16-bit register pair HL. The only 8-bit ALU operations that can have a destination other than the accumulator are the unary incrementation or decrementation instructions, which can operate on any 8-bit register or on memory addressed by HL, as for two-operand 8-bit operations. Direct copying is supported between any two 8-bit registers and between any 8-bit register and an HL-addressed memory cell, using the MOV instruction. An immediate value can also be moved into any of the foregoing destinations, using the MVI instruction. Due to the regular encoding of the MOV instruction (using nearly a quarter of the entire opcode space) there are redundant codes to copy a register into itself (''MOV B,B'', for instance), which are of little use, except for delays.Even so, there is no need for seven different effectively identical delay instructions, and they are also identical in effect and form to the NOP instruction, except that NOP conveniently has the opcode 00 hex. However, what would have been a copy from the HL-addressed cell into itself (i.e., ''MOV M,M'') instead encodes the HLT instruction, halting execution until an external reset or unmasked interrupt occurs.(The TRAP interrupt, being an NMI, can always bring the 8085 out of the HALT state.)


16-bit operations

Although the 8085 is an 8-bit processor, it has some 16-bit operations. Any of the three 16-bit register pairs (BC, DE, HL) or SP can be loaded with an immediate 16-bit value (using LXI), incremented or decremented (using INX and DCX), or added to HL (using DAD). LHLD loads HL from directly addressed memory and SHLD stores HL likewise. The XCHG operation exchanges the values of HL and DE. XTHL exchanges last item pushed on stack with HL. Adding HL to itself performs a 16-bit arithmetic left shift with one instruction. The only 16-bit instruction that affects any flag is DAD (adding BC, DE, HL, or SP to HL), which updates the carry flag to facilitate 24-bit or larger additions and left shifts. Adding the stack pointer to HL is useful for indexing variables in (recursive) stack frames. A stack frame can be allocated using DAD SP and SPHL, and a branch to a computed pointer can be done with PCHL. These abilities make it feasible to compile languages such as PL/M, Pascal, or C with 16-bit variables and produce 8085 machine code. Subtraction and bitwise logical operations on 16 bits is done in 8-bit steps. Operations that have to be implemented by program code (subroutine libraries) include comparisons of signed integers as well as multiplication and division.


Undocumented instructions

A number of undocumented instructions and flags were discovered by two software engineers, Wolfgang Dehnhardt and Villy M. Sorensen in the process of developing an 8085 assembler. These instructions use 16-bit operands and include indirect loading and storing of a word, a subtraction, a shift, a rotate, and offset operations. By the time 8085 was designed but not yet announced, many designers found it to be inferior to the competing products already on the market. The next generation 16-bit 8086 CPU was already in development. Intel made a last minute decision to leave 10 out of 12 new 8085 instructions undocumented to speed up and simplify the design of the upcoming 8086 CPU.


Input/output scheme

The 8085 supports both port-mapped and memory-mapped I/O. It supports up to 256
input/output In computing, input/output (I/O, i/o, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, such as another computer system, peripherals, or a human operator. Inputs a ...
(I/O) ports via dedicated Input/Output instructions, with port addresses as operands. Port-mapped IO can be an advantage on processors with limited address space. During a port-mapped I/O bus cycle, the 8-bit I/O address is output by the CPU on both the lower and upper halves of the 16-bit address bus. Devices designed for memory mapped I/O can also be accessed by using the LDA (load accumulator from a 16-bit address) and STA (store accumulator at a 16-bit address specified) instructions, or any other instructions that have memory operands. A memory-mapped IO transfer cycle appears on the bus as a normal memory access cycle.


Development system

Intel produced a series of development systems for the 8080 and 8085, known as the MDS-80 Microprocessor System. The original development system had an 8080 processor. Later 8085 and 8086 support was added including ICE ( in-circuit emulators). It is a large and heavy desktop box, about a 20" cube (in the Intel corporate blue color) which includes a CPU, monitor, and a single 8-inch floppy disk drive. Later an external box was made available with two more floppy drives. It runs the
ISIS Isis was a major goddess in ancient Egyptian religion whose worship spread throughout the Greco-Roman world. Isis was first mentioned in the Old Kingdom () as one of the main characters of the Osiris myth, in which she resurrects her sla ...
operating system and can also operate an
emulator In computing, an emulator is Computer hardware, hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run sof ...
pod and an external
EPROM An EPROM (rarely EROM), or erasable programmable read-only memory, is a type of programmable read-only memory (PROM) integrated circuit, chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored d ...
programmer. This unit uses the Multibus card cage which was intended just for the development system. A surprising number of spare card cages and processors were being sold, leading to the development of the Multibus as a separate product. The later iPDS is a portable unit, about 8"16"20", with a handle. It has a small green screen, a keyboard built into the top, a 5ÂĽ inch floppy disk drive, and runs the ISIS-II operating system. It can also accept a second 8085 processor, allowing a limited form of multi-processor operation where both processors run simultaneously and independently. The screen and keyboard can be switched between them, allowing programs to be assembled on one processor (large programs took a while) while files are edited in the other. It has a
bubble memory Bubble memory is a type of non-volatile memory, non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as ''bubbles'' or ''domains'', each storing one bit of data. The material is arrange ...
option and various programming modules, including EPROM, and Intel 8048 and 8051 programming modules which are plugged into the side, replacing stand-alone device programmers. In addition to an 8080/8085 assembler, Intel produced a number of compilers including those for PL/M-80 and Pascal, and a set of tools for linking and statically locating programs to enable them to be burned into
EPROM An EPROM (rarely EROM), or erasable programmable read-only memory, is a type of programmable read-only memory (PROM) integrated circuit, chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored d ...
s and used in
embedded system An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is e ...
s. A lower cost "MCS-85 System Design Kit" (SDK-85) board contains an 8085 CPU, an 8355 ROM containing a debugging monitor program, an 8155 RAM and 22 I/O ports, an 8279 hex keypad and 8-digit 7-segment LED, and a TTY (Teletype) current loop serial interface. Pads are available for one more 2KĂ—8 8755 EPROM, and another RAM 8155 I/O Timer/Counter can be optionally added. All data, control, and address signals are available on dual pin headers, and a large prototyping area is provided.


List of Intel 8085 Models


Applications

The 8085 processor was used in a few early personal computers, for example, the TRS-80 Model 100 line used an OKI manufactured 80C85 (MSM80C85ARS). The
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss ", , ) is a type of MOSFET, metal–oxide–semiconductor field-effect transistor (MOSFET) semiconductor device fabrication, fabrication process that uses complementary an ...
version 80C85 of the NMOS/HMOS 8085 processor has several manufacturers. In the
Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
, an 80C85 clone was developed under the designation IM1821VM85A () 2016 was still in production. Some manufacturers provide variants with additional functions such as additional instructions. The radiation hardened version of the 8085 has been in on-board instrument data processors for several
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
and ESA space physics missions in the 1990s and early 2000s, including CRRES, Polar, FAST, Cluster, HESSI, the
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Mars Rover, and
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. The Swiss company SAIA used the 8085 and the 8085–2 as the CPUs of their PCA1 line of
programmable logic controller A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that ...
s during the 1980s. Pro-Log Corp. put the 8085 and supporting hardware on an STD Bus format card containing CPU, RAM, sockets for ROM/EPROM, I/O and external bus interfaces. The included Instruction Set Reference Card uses entirely different mnemonics for the Intel 8085 CPU. The product was a direct competitor to Intel's Multibus card offerings. second source In the electronics industry, a second source is a company that is licensed to manufacture and sell components originally designed by another company (the first source). It is common for engineers and purchasers to seek components that are availab ...
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AMD Advanced Micro Devices, Inc. (AMD) is an American multinational corporation and technology company headquartered in Santa Clara, California and maintains significant operations in Austin, Texas. AMD is a hardware and fabless company that de ...
Am9085 image:Ic-photo-Mitsubishi--M5L8085AP--(8085-CPU).png,
Mitsubishi The is a group of autonomous Japanese multinational companies in a variety of industries. Founded by YatarĹŤ Iwasaki in 1870, the Mitsubishi Group traces its origins to the Mitsubishi zaibatsu, a unified company that existed from 1870 to 194 ...
M5L8085 image:NEC D8085A 1a.jpg, NEC ÎĽPD8085 image:Soviet made processor KM1821VM85A.jpg, NZPP Novosibirsk IM1821VM85 (Soviet Union) image:Ic-photo-OKI--M80C85A-2--(8085-CPU).JPG, OKI M80C85 image:Siemens SAB8085A C 1.jpg,
Siemens Siemens AG ( ) is a German multinational technology conglomerate. It is focused on industrial automation, building automation, rail transport and health technology. Siemens is the largest engineering company in Europe, and holds the positi ...
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Toshiba is a Japanese multinational electronics company headquartered in Minato, Tokyo. Its diversified products and services include power, industrial and social infrastructure systems, elevators and escalators, electronic components, semiconductors ...
TMP8085


MCS-85 family

The 8085 CPU is one part of a family of chips developed by Intel for building a complete system. Many of these support chips were also used with other processors. The original IBM PC based on the Intel 8088 processor used several of these chips; the equivalent functions today are provided by VLSI chips, namely the " Southbridge" chips. * 8085 – CPU * 8231 – Arithmetic Processing Unit * 8232 – Floating-Point Processor * 8205 – 1 of 8 Binary Decoder


Static RAM

* 8155 – 2K-bit static MOS RAM with 3 I/O Ports and Timer. Multiplexed address/data. Active low CE. The industrial version of ID8155 was available for in quantities of 100 and up.Intel Corporation, "8086 Available for industrial environment", Intel Preview Special Issue: 16-Bit Solutions, May/June 1980, p. 29. The military version of M8155 was available for in quantities of 100. There is a version of Intel 8155–2. The available 8155H was introduced using the HMOS II technology which it uses 30 percent less power than the previous generation. The plastic package version of P8155H (3 MHz) and P8155H-2 (5 MHz) are available for and per 100 in quantities respectively. * 8156 – 2K-bit static MOS RAM with 3 I/O Ports and Timer. Multiplexed address/data. Active high CE. The industrial version of ID8156 was available for in quantities of 100. There is a version of Intel 8156–2. The available 8156H was introduced using the HMOS II technology which it uses 30 percent less power than the previous generation. The plastic package version of P8156H (3 MHz) and P8156H-2 (5 MHz) are available for and per 100 in quantities respectively. * 8185 – 1,024 x 8-bit static RAM packaged in a compact 18-pin DIP. It includes three chip selects and an internal address latch driven directly by the 8085's ALE. The version of Intel 8185-2 was available for in quantity of 100.


ROM memory

* 8355 – 2,048 × 8-bit ROM, two 8-bit I/O ports. Multiplexed address/data. The industrial version of ID8355 was available for in quantities of 1000. There is a version of Intel 8355–2. * 8755 – 2048 x 8-bit
EPROM An EPROM (rarely EROM), or erasable programmable read-only memory, is a type of programmable read-only memory (PROM) integrated circuit, chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored d ...
, two 8-bit I/O ports. Multiplexed address/data. The Intel 8755A-2 is the version. That version was available for in quantity of 100. There was an Industrial Grade version Intel I8755A-8.


RAM controllers

* 8202 – Dynamic RAM Controller. This supports the Intel 2104A, 2117, or 2118 DRAM modules, up to 128 KB of DRAM modules. Price was reduced to for quantities of 100 for the D8202 package style around May 1979. * 8203 – Dynamic RAM Controller. The Intel 82C03 CMOS version dissipates less than 25 mA. It supports . It refreshes every 10 to 16 microseconds. It supports multiplexing of row and column memory addresses. It generates strobes to latch the address internally. It arbitrates between simultaneous requests for memory access and refresh. It also acknowledges memory-access cycles to the system CPU. The 82C03 was available in either ceramic or plastic packages for in 100 pieces quantity. * 8207 – DRAM Controller


Periphery

* 8206 – Error Detection & Correction Unit * 8210 – TTL To MOS Shifter & High Voltage Clock Driver * 8212 – 8-bit I/O Port. The industrial version of ID8212 was available for in quantities of 100. * 8216 – 4-bit Parallel Bidirectional Bus Driver. The industrial version of ID8216 was available for in quantities of 100. * 8218/8219 – Bus Controller * 8226 – 4-bit Parallel Bidirectional Bus Driver. The industrial version of ID8226 was available for in quantities of 100. * 8237 – DMA Controller * 8251 – USART Communication Controller * 8253 – Programmable Interval Timer * 8254 – Programmable Interval Timer. The 82C54 CMOS version was outsourced to Oki Electronic Industry Co., Ltd. * 8255 – Programmable Peripheral Interface * 8256 – Multifunction Peripheral. This multifunction chip uses
Serial Communications In telecommunication and data transmission, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits ar ...
, Parallel I/O, Counter/Timers and
Interrupt In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted ...
s. The Intel 8256AH was available for in quantities of 100. This integrated circuit chip integrates the chips with the following functionality: ** Intel 8251A Programmable Communications Interface ** Intel 8253 Programmable Interval Timer ** Intel 8255A Programmable Peripheral Interface ** Intel 8259A Programmable Interrupt Controller. * 8257 – DMA Controller * 8259 –
Programmable Interrupt Controller In computing, a programmable interrupt controller (PIC) is an integrated circuit that helps a microprocessor (or CPU) handle interrupt requests (IRQs) coming from multiple different sources (like external I/O devices) which may occur simultane ...
* 8271 – Programmable Floppy Disk Controller * 8272 – Single/Double Density Floppy Disk Controller. It is compatible with IBM 3740 and System 34 formats and provides both
Frequency Modulation Frequency modulation (FM) is a signal modulation technique used in electronic communication, originally for transmitting messages with a radio wave. In frequency modulation a carrier wave is varied in its instantaneous frequency in proporti ...
(FM) or Modified Frequency Modulation (MFM). This version was available for in quantities of 100.Intel Corporation, "Intel peripherals enhance 8086 system design", Intel Preview Special Issue: 16-Bit Solution, May/June 1980, p. 22. * 8273 – Programmable
HDLC High-Level Data Link Control (HDLC) is a communication protocol used for transmitting data between devices in Telecommunications, telecommunication and Computer network, networking. Developed by the International Organization for Standardization ...
/ SDLC Protocol Controller. This device supports ISO/
CCITT The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is one of the three Sectors (branches) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunicat ...
's HDLC and IBM's SDLC communication protocols. These were available for () and () in quantities of 100. * 8274 – Multi-Protocol Serial Controller. This support three different protocols using the following feature of Asynchronous Operation, Byte Synchronous Operation and Bit Synchronous Operation. The Byte Synchronous mode is compatible to IBM's Bisync signal protocol. The Bit Synchronous mode is compatible to IBM's SDLC and the International Standards Organization's
HDLC High-Level Data Link Control (HDLC) is a communication protocol used for transmitting data between devices in Telecommunications, telecommunication and Computer network, networking. Developed by the International Organization for Standardization ...
protocol and is compatible with CCITT X.25 international standard as well. It was packaged in 40-pin product using the Intel's HMOS technology. The available version is rated up to 880 kilobaud for in the quantities of 100. NEC μPD7201 was also compatible. * 8275 – Programmable CRT Controller. It refreshes the raster scan display by buffering from main memory and keeping track of the display portion. This version was available for in quantities of 100. * 8276 – Small System CRT Controller * 8278 – Programmable Key Board Interface * 8279 – Key Board/Display Controller * 8282 – 8-bit Non-Inverting Latch with Output Buffer * 8283 – 8-bit Inverting Latch with Output Buffer * 8291 –
GPIB Glycoprotein Ib (GPIb), also known as CD42, is a component of the GPIb-V-IX complex on platelets. The GPIb-V-IX complex binds von Willebrand factor, allowing platelet adhesion and platelet plug formation at sites of vascular injury. Glycoprotei ...
Talker/Listener. This controller can operate from 1 to . It was available for in quantities of 100. * 8292 –
GPIB Glycoprotein Ib (GPIb), also known as CD42, is a component of the GPIb-V-IX complex on platelets. The GPIb-V-IX complex binds von Willebrand factor, allowing platelet adhesion and platelet plug formation at sites of vascular injury. Glycoprotei ...
Controller. Designed around Intel 8041A which it has been programmed as an controller interface element. It also controls the bus using three lock-up timers to detect issues on the GPIB bus interface. It was available for in quantities of 100. * 8293 – GPIB Transceiver. This chipset supports up to 4 different modes: Mode 0 Talker/Listener Control Lines, Mode 1 Talker/Listener/Controller Control Lines, Mode 2 Talker/Listener/Controller Data Lines, and Mode 3 Talker/Listener Data Lines. It was available for in quantities of 100. At the time of release, it was available in samples then full production in the first quarter of 1980.Intel Corporation, "Feature: 8293 Transceiver completes Intel GPIB family", Intel Preview, January/February 1980, p. 13. * 8294 – Data Encryption/Decryption Unit + 1 O/P Port. It encrypts and decrypts 64-bit blocks of data using the Federal Information Processing Data Encryption Standard algorithm. This also uses the
National Bureau of Standards The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical sc ...
encryption algorithm. This DEU operates using a 56-bit user-specified key to generate 64-bit cipher words. It was available for in quantities of 100. * 8295 – Dot Matrix Printer Controller. This interfaces with LRC 7040 Series dot matrix printers and other small printers as well. It was available for in quantities of 100.


Educational use

In many engineering schools the 8085 processor is used in introductory microprocessor courses. Trainer kits composed of a printed circuit board, 8085, and supporting hardware are offered by various companies. These kits usually include complete documentation allowing a student to go from soldering to assembly language programming in a single course. Also, the architecture and instruction set of the 8085 are easy for a student to understand. Shared Project versions of educational and hobby 8085-based
single-board computer A single-board computer (SBC) is a complete computer built on a single circuit board, with microprocessor(s), memory, input/output (I/O) and other features required of a functional computer. Single-board computers are commonly made as demonst ...
s are noted below in the External Links section of this article.


Simulators

Software simulators are available for the 8085 microprocessor, which allow simulated execution of opcodes in a graphical environment.


See also

* IBM System/23 Datamaster gave IBM designers familiarity with the 8085 support chips used in the
IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the List of IBM Personal Computer models, IBM PC model line and the basis for the IBM PC compatible ''de facto'' standard. Released on ...
.


Notes


References


Further reading

;Books * * * * Bill Detwiler ''Tandy TRS-80 Model 100 Teardown'' Tech Republic, 2011 Web * ; 495 pages * ; 466 pages * ; 303 pages ;Reference Cards * ''Intel 8085 Reference Card''; Saundby; 2 pages. (archive)
/small>
Intel 8080 / 8085 Assembly Reference Card (HEX opcodes)


External links

* Simulators:
GNUSim8085
- simulator, assembler, debugger Boards:
MCS-85 System Design Kit (SDK-85)
- Intel
Altaids

SBC-85

Minimax

Glitchworks

OMEN Alpha
{{Authority control 8085 8-bit microprocessors Computer-related introductions in 1977