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The X-Philes (2nd Revision)
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The X-Philes Number 1 (1995).iso
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hp48hor2
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in7.doc
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1995-03-31
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(Library.development)
Item: 16 by akcs.bson@hpcvbbs.cv.hp.com
Author: [Jan Brittenson]
Date: Wed Feb 05 1992
[Note: What Jan here refers to (using Alonzo Gariepy's mnemonics) as
the "IN.4 A" instruction, is the same as the "A=IN" instruction in
HP's mnemonics. Either way, it's opcode 802 (hex). -jkh-]
Due to a bug in the Saturn CPU (or maybe the memory controller, or the
interconnect between them, or whatever, what do I know...) IN.4 A
*must* reside on an even address, or the next instruction will be
garbled. The solution is to call the ROM at address 1160. So, replace:
IN.4 A
with:
CALL 0x1160 ; do IN.4 A
[That's GOSBVL #1160 in HP mnemonics. -jkh-]
The code at 1160 just does an IN.4 A followed by a RET. Since it's ROM
it will always be on an even (integral byte) address.