Below is the complete write-up on the 6702 chip. If I missed anything, or if anythhing is wrong, let me know. -------------------------------------------------------------------------- 6702 Functional Description REGISTERS Input Register - 8 bits Even/Odd Register - 1 bit internal register. Inverse of bit 0 of the previous value of the input register. Last Number Register - 8 bit internal register. Previous number accepted by the 6702. Shift Registers - Eight internal circular shift registers of different lengths, one for each data bit. bit 0 length 6 bit 1 length 3 bit 2 length 7 bit 3 length 8 bit 4 length 1 bit 5 length 3 bit 6 length 5 bit 7 length 2 Flip-flops - Eight flip-flops, one for the output of each shift register. The output of the flip-flops constitute the output register. INITIALIZATION The Last Number Register and the Flip-flops are initialized to 214. Everything else is initialized to zero. OPERATION On reset, 214 is output. The output remains the same until the 6702 receives an even number followed by an odd number. The even number is not used. The odd number is used to calculate a new output. Input other than the even-odd sequence is ignored. INTERNAL OPERATION 1. When data is written to the 6702, the low bit is AND'ed with the Even/Odd register. If the result is zero, the low bit is inverted and written to the Even/Odd register, and the 6702 waits for more input. If the result is one, operation continues below. 2. The input register is exclusive OR'ed with the Last Number register. 3. That result is exclusive OR'ed with the current position of the shift registers. 4. The shift registers are shifted one position. The input register is copied to the Last Number register. The low bit of the input register is inverted and written to the Even/Odd register. 5. The shift registers are output to the flip-flops. For every bit that is one, the output state of the flip-flops is toggled. NOTE The original SuperPET contains sockets for four 6702 daughter boards. Other variations of the 6702 may have been planed for use with other software. Different initialization values and/or different shift register lengths would generate entirely different sequences of numbers. --------------------------------------------------------------------------- wlevak@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org Message was sent through the cbm-hackers mailing listReceived on 2012-09-05 07:00:11
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