[fa.info-cpm] Godbout SS I

C70:info-cpm (05/15/82)

>From goldfarb.ucf-cs@Udel-Relay Sat May 15 00:35:58 1982
The following is forwarded from USENET net.micro group.

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>From duke!decvax!ucbvax!ARPAVAX:CAD:teklabs!tekmdp!patc Wed May 12 09:04:08 1982
Subject: Help Sys Support I
Newsgroups: net.micro
Status: RO


I need help with my Goubout System Support - I.
	I have a nearly full blown System Support - I board.  There is
one Ram chip in the ROM/RAM chip sockets addressed as global memory at
0F000H - 0FFFFH. My CPU is a Z-80 but has special circuitry to mirror
I/O port addresses on the high address lines during IN and OUT
instructions. If I address an I/O port in the range 0F0H to 0FFH, the
system Support 1 enables the buss drivers for the data lines but does
not select the RAM.  This causes interference with the input/output
data.
	When I modify the jumpers so an I/O address is not mirrored,
it's even worse. The problem seems to depend on the type of IN/OUT
instruction and the contents of the A or B register whether or not the
board is enabled.
	Has anyone else encountered this problem? If so is there a fix
for it. I do not use or need the battery backup for the RAM.
			Pat Caudill
			decvax!teklabs!tekmdp!patc
			ucbvax!teklabs!tekmdp!patc
			ARPANET:  ucbvax!teklabs!tekmdp!patc @ ucb-c70

C70:info-cpm (05/16/82)

>From FJW@Mit-Mc Sat May 15 23:22:04 1982
The mirror problem is easily solved as follows - please pass this on
to the original requestor:

	ld	a,data
	ld	b,port-address
	ld	c,b
	out	(c),a

--Frank