andrew@frip.wv.tek.com (Andrew Klossner) (04/21/89)
[This is really just nit picking.]
"The Z80 will handle interrupts inside of block moves ..."
This isn't really the case.
The way that the Z80 block move (is it spelled LDIR?) instruction works is:
-- move one byte from here to there
-- decrement the PC
Yep, it refetches the instruction for each byte.
It looks like a long interruptible instruction, but it's actually a
self-looping non-interruptible instruction.
A good example of an interruptible instruction is block transfer
("BLT") on the PDP-10. Its three operands are initial source address,
initial destination address, and one of the end addresses. The initial
addresses are stored in the two halves of a register. If an interrupt
happens, the register is updated so that the two addresses indicate
where to resume, and the saved PC points to the BLT.
[Now somebody will pop my bubble and tell me the PDP-10 used the Z80
self-looping hack ...]
-=- Andrew Klossner (uunet!tektronix!orca!frip!andrew) [UUCP]
(andrew%frip.wv.tek.com@relay.cs.net) [ARPA]