Z80 TRAP and CP/M

Jim Battle frustum at pacbell.net
Sun Apr 2 18:52:10 CDT 2006


Chuck Guzis wrote:
> Although I've written several CP/M CBIOSes, I've never had to write one on
> a system that used the Trap vector (0066h) for something essential.
> 
> Just curious--has anyone had to deal with servicing the Trap interrupt in
> CP/M?  How does one keep CP/M from clobbering the vector, since it's in the
> FCB2 area?
>

Chuck, I have no answer for you, but it reminds me of a point I've 
always wondered about.  The CP/M service call to 0005 takes three bytes 
-- why didn't they move it three bytes forward so that the one byte "RST 
1" call could have been used instead?




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