MOS Technology 6507

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UMC UM6507 (= MOS 6507).

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 Atari 2600

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.^[1]
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 ROM 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 computers based on the 650x architecture, used either the standard 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 into the early 1990s, as it wasn't discontinued until January 1, 1992.

Pin configuration

Pin Layout of MOS 6507^[2]

/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 on the processor.

References

1. Visual6502. "Visual6502.org: 6502 vs. 6507".
2. Peter Turnbull (January 25, 2005). "MOS 6507 Tech Spec's".^{[dead link]}

[hide] v t e 65xx-series CPUs from MOS Technology, second source/clone vendors, and the Western Design Center MOS 6501 MOS 6502 WDC 65C02 Hudson HuC6280 Ricoh 2A03 MOS 6507 MOS 6508 MOS 6509 MOS 6510 (and 7501, 8500, 8501) MOS 8502 CSG 65CE02 (and 4510) WDC 65802 WDC 65816 Ricoh 5A22 Nintendo SA-1

Categories:

• 65xx microprocessors
• MOS microprocessors