See all the fun I missed by buying the wrong 7854 version!
So then the flag pin would be pulled high by the pullup. I traced the address
decoding out once but did not keep any notes. I initially assumed the flag
signal needs to be set either high or low but now having looked at it again I
was not sure.
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On Mon, 20 Jan 2014 11:43:25 -0700, you wrote:
No, you do not need to do anything like that if you use the Pentti
Haka ROM images from my site. Just pull out the FPLA/FPRP.
On Mon, Jan 20, 2014 at 10:37 AM, David <davidwhess@...> wrote:
The FPRP is different from the original FPLA in that the chip enable input which
enables the outputs is replaced with a flag output which is used to disable the
ROMs when an FPRP address is decoded. If the FPRP is removed, then the flag
output has to be set to not disable the ROMs which is just one jumper.
Normally the flag output, pin 19, would be tied to ground, pin 9, but in this
case Tektronix did something a little more complicated because the flag output
disables 13 bits of addresses which the FPRP replaces, disables the main ROMs,
and allows the patch ROMs to be enabled so it may need to be tied to another
spot to get the address decoding correct.
David Hess