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]