8 Dec
2005
8 Dec
'05
3:43 p.m.
On Dec 8 2005, 16:26, Jim Leonard wrote:
Allison wrote:
1970s so my
You lived a shelterd life.
I lived a young life. I first became of programming age in late first CPUs were 6502, Z80, 68000, and 808x.
Whether it's called a Half Carry or an Auxiliary Carry seems to depend
somewhat on whose data book you read. I've seen both used for the Z80
for example, indifferent manuals.
...in a 6800, it's called the Auxiliary Carry; in a 6809 it's called a
Half Carry. It's bit 5 of the status register in both.
...in a Z80 and 8086 it's called the Auxiliary Carry; it's bit 4 in the
Flags register in these and 8080/8085.
...it's bit 5 in 8048 and 8051 series micrcontrollers.
There's no (visible) equivalent in a 6502 because of the way its
special Decimal Mode for BCD arithmetic works. Ditto for a 68000.
There isn't one in an ARM either.
--
Pete Peter Turnbull
Network Manager
University of York