MOS Technology 6507
Encyclopedia
The 6507 is an 8-bit microprocessor
from MOS Technology, Inc.
It is essentially a 6502
chip in a smaller, cheaper 28-pin package. 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 8 KB
of memory, which at the time (1975) was not considered restrictive.
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 that they are not vulnerable to generating spurious interrupts from stray 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.
The 6507 was only widely used in two applications, the best-selling Atari 2600
video game console
and the Atari 8-bit family
floppy disk
controllers for the 810 and 1050 drives. In the 2600, the system was further limited by the design of the cartridge slot, which allowed for only 4KB of external memory to be addressed (the other 4KB was reserved for the internal RAM and I/O chip).
Most other machines, notably home computer
s based on the 650x architecture, used either the "full" 6502 or extended, rather than cut down, versions of it, in order to allow for more memory.
By the time the 6502 line was becoming widely used around 1980, ROM
and RAM
semiconductor
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 contained it continued to be sold until the end of the 1980s.
The 6507 uses a 28-pin configuration, with 13 pins in use for addressing, and 8 for data. The seven remaining pins are used for power, clock cycles, to indicate reset or ready, and control the read/write request from the CPU. There is no IRQ or NMI
on the processor.
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
from MOS Technology, Inc.
MOS Technology
MOS Technology, Inc., also known as CSG , was a semiconductor design and fabrication company based in Norristown, Pennsylvania, in the United States. It is most famous for its 6502 microprocessor, and various designs for Commodore International's range of home computers.-History:MOS Technology, Inc...
It is essentially a 6502
MOS Technology 6502
The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
chip in a smaller, cheaper 28-pin package. 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 8 KB
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
of memory, which at the time (1975) was not considered restrictive.
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 that they are not vulnerable to generating spurious interrupts from stray 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.
The 6507 was only widely used in two applications, the best-selling Atari 2600
Atari 2600
The Atari 2600 is a video game console released in October 1977 by Atari, Inc. It is credited with popularizing the use of microprocessor-based hardware and cartridges containing game code, instead of having non-microprocessor dedicated hardware with all games built in...
video game console
Video game console
A video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device to display a video game...
and the Atari 8-bit family
Atari 8-bit family
The Atari 8-bit family is a series of 8-bit home computers manufactured from 1979 to 1992. All are based on the MOS Technology 6502 CPU and were the first home computers designed with custom coprocessor chips...
floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
controllers for the 810 and 1050 drives. In the 2600, the system was further limited by the design of the cartridge slot, which allowed for only 4KB of external memory to be addressed (the other 4KB was reserved for the internal RAM and I/O chip).
Most other machines, notably home computer
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly 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 single nontechnical user...
s based on the 650x architecture, used either the "full" 6502 or extended, rather than cut down, versions of it, in order to allow for more memory.
By the time the 6502 line was becoming widely used around 1980, ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
and RAM
Random-access memory
Random access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in...
semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
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 contained it continued to be sold until the end of the 1980s.
Pin configuration
| /RES | 1 | 28 | Ph2 out |
| Vss | 2 | 27 | Ph0 in |
| RDY | 3 | 26 | R/W |
| Vcc | 4 | 25 | D0 |
| A0 | 5 | 24 | D1 |
| A1 | 6 | 23 | D2 |
| A2 | 7 | 22 | D3 |
| A3 | 8 | 21 | D4 |
| A4 | 9 | 20 | D5 |
| A5 | 10 | 19 | D6 |
| A6 | 11 | 18 | D7 |
| A7 | 12 | 17 | A12 |
| A8 | 13 | 16 | A11 |
| A9 | 14 | 15 | A10 |
The 6507 uses a 28-pin configuration, with 13 pins in use for addressing, and 8 for data. The seven remaining pins are used for power, clock cycles, to indicate reset or ready, and control the read/write request from the CPU. There is no IRQ or NMI
Non-Maskable interrupt
A non-maskable interrupt is a computer processor interrupt that cannot be ignored by standard interrupt masking techniques in the system. It is typically used to signal attention for non-recoverable hardware errors...
on the processor.