49
edits
Z80: Difference between revisions
From Sinclair Wiki
→Bits 3 and 5 of the F register: Add some clarifications for memptr_eng.txt.
(→Instruction set: Swap Cyrillic and Latin names for U880D. Add a bit on the UB880D and UA880D) |
(→Bits 3 and 5 of the F register: Add some clarifications for memptr_eng.txt.) |
||
| Line 26: | Line 26: | ||
Woody has confirmed that bits 3 and 5 of the flags are copied on all BIT instructions on both a Zilog Z80 and an NEC clone (stated on the link above as being "unverified"). | Woody has confirmed that bits 3 and 5 of the flags are copied on all BIT instructions on both a Zilog Z80 and an NEC clone (stated on the link above as being "unverified"). | ||
==== Clarifications ==== | |||
Some bits which aren't immediately clear from memptr_eng.txt but appear to be generally true: | |||
* MEMPTR is unchanged for DJNZ with B == 1 or for a conditional JR when the jump is not taken. (Note the difference with conditional JP and CALL where MEMPTR is set even if the jump isn't taken). | |||
* MEMPTR is set for IN <register>, (C) and OUT (C), <register> for all registers, not just A. | |||
==== Clarification needed ==== | |||
* What is the value of MEMPTR after IN A, 255? Everywhere else that the high byte of MEMPTR is set to A, there is no carry from the low byte (eg LD (nnnn), A), but memptr_eng.txt implies there is a carry in this case. Has anyone checked this case? | |||
=== SCF and CCF === | === SCF and CCF === | ||
