The 6507 (typically "''sixty-five-oh-seven''" or "''six-five-oh-seven''") is an 8-bit

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 ...

from MOS Technology, Inc. It is a version of their 40-pin

6502 The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small ...

packaged in a 28-pin DIP, making it cheaper to package and integrate in systems. The reduction in pin count is achieved by reducing the

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 ...

from 16 bits to 13 (limiting the available memory range from 64 KB to 8KB) and removing a number of other pins used only for certain applications. To do this, A15 to A13 and some other signals such as the interrupt lines are not accessible. As a result, it can only address 8KB of memory, which for some applications at the time (1975) was acceptable and not overly restrictive. The entire 6500 CPU family was originally conceived as a line of very low-cost microprocessors for small-scale embedded systems. The 6507 and 6502 chips use the same underlying silicon layers, and differ only in the final metallisation layer. This ties the interrupt lines to their inactive level so they are not vulnerable to generating spurious interrupts from noise. The first three digits of the chip identifier are part of the silicon layers, and the final digit is in the metallisation layer. Micro-photography of the 6502 and 6507 shows this difference. Atari-2600-Console

The 6507 is widely used in two applications: the best-selling

Atari 2600 The Atari 2600 is a home video game console developed and produced by Atari, Inc. Released in September 1977 as the Atari Video Computer System (Atari VCS), it popularized microprocessor-based hardware and games stored on swappable ROM cartridg ...

video game console A video game console is an electronic device that Input/output, outputs a video signal or image to display a video game that can typically be played with a game controller. These may be home video game console, home consoles, which are generally ...

and peripherals for the

Atari 8-bit computers The Atari 8-bit computers, formally launched as the Atari Home Computer System, are a series of home computers introduced by Atari, Inc., in 1979 with the Atari 400 and Atari 800. The architecture is designed around the 8-bit MOS Technology 650 ...

including the

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Serial & Parallel Interface, and the

810 __NOTOC__ Year 810 ( DCCCX) was a common year starting on Tuesday of the Julian calendar. Events By place Byzantine Empire * Spring – The Venetian dukes change sides again, submitting to King Pepin, under the authority of hi ...

and

1050 Year 1050 ( ML) was a common year starting on Monday of the Julian calendar. Events By place Europe * Hedeby in Jutland is sacked by King Harald Hardrada of Norway, during the course of a conflict with Sweyn II of Denmark. * King Anu ...

disk drives. In the 2600, the system is further limited by the design of the

ROM cartridge A ROM cartridge, usually referred to in context simply as a cartridge, cart, cassette, or card, is a replaceable part designed to be connected to a consumer electronics device such as a home computer, video game console or, to a lesser extent, ...

slot, which only allows for 4KB of the external memory to be addressed. The other 4KB is reserved for the internal

RAM Ram, ram, or RAM most commonly refers to: * A male sheep * Random-access memory, computer memory * Ram Trucks, US, since 2009 ** List of vehicles named Dodge Ram, trucks and vans ** Ram Pickup, produced by Ram Trucks Ram, ram, or RAM may also ref ...

and I/O chips, using a minimal-cost partial decoding technique that causes the RAM and peripheral device registers to appear at multiple aliased addresses throughout the 4K address space. Most other machines, notably

home computer Home computers were a class of microcomputers that entered the market in 1977 and became common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a s ...

s based on the 650x architecture, use either the standard 6502 or extended versions of it, in order to allow for more memory. By the time the 6502 line was becoming widely used around 1980,

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...

and RAM

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memory prices had fallen to the point where the 6507 was no longer a worthwhile simplification. Its use in new designs ceased at that point, though the Atari 2600 that contains it continued to be sold into the early 1990s, as it was not discontinued until January 1, 1992. However, late-model Atari 2600 consoles do not necessarily contain a discrete 6507 chip.

Pin configuration

The 6507 uses a 28-pin configuration, with 13 address pins (A0..A12) and 8 data pins (D0..D7). The seven remaining pins are used for power (Vss, Vcc), the CPU timing clock (φ0, φ2), to reset the CPU (the /RES pin), to request a CPU wait state during its next memory read access (the RDY pin), and for the CPU to indicate if a read or write memory (or

MMIO Memory-mapped I/O (MMIO) and port-mapped I/O (PMIO) are two complementary methods of performing input/output (I/O) between the central processing unit (CPU) and peripheral devices in a computer (often mediating access via chipset). An alterna ...

device) access is being performed (the R/W pin). There is no IRQ or NMI pin on the processor. The RDY pin is not included on all other 28-pin cut-down versions of the 6502. Within the Atari 2600, RDY is used to synchronise the CPU to the television video lines. This function is essential for the 'racing the beam' method used by the 6502 and Atari

Television Interface Adaptor The Television Interface Adaptor (TIA) is the custom computer chip which, along with a variant of the MOS Technology 6502, constitutes the heart of the 1977 Atari Video Computer System game console. The TIA generates the screen display, sound ...

chip to generate the television video signal. In response to a specific address access, the TIA will assert RDY to halt the CPU until the end of the current video scan line.

Pin configuration

References

Further reading