Questions tagged [registers]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
8
votes
1answer
104 views

Is scratchpad register 15 directly addressable on the F3850 (except as QL)?

The Fairchild F8 CPU, the F3850, has 64 scratchpad registers. The first 12 of these are directly addressable by several instructions. For example, the opcodes $CX add the contents of scratchpad ...
5
votes
2answers
304 views

Why when outputting registers' value the result is a wrong fluctuating value in a Z80 CPU?

I got an EEPROM AT28C64 and loaded it with instructions with my handmade STM32 EEPROM programmer, the instructions are very simple: Load A register with decimal number 85 which is, in binary, ...
3
votes
1answer
188 views

How are the index registers on the Censor 932 accessed?

The Censor 932 CPU architecture has one instruction type that takes a 3-bit "index register" field, but looking at the rest of the instruction set, I can't see any instructions that read, write, or ...
14
votes
3answers
2k views

Why do only the low 7-bits of the R register increment?

On the Z80 the R register is 8 bits wide, as evidenced by LD A,R and LD R,A And every M1 cycle, R increments by 1. But the uppermost bit does not participate in this increment. R will not go from 0x7F ...