plasmo Messages: 916 Registered: March 2017 Location: New Mexico, USA
Senior Member
Andrew,
I have a jumper that set TEST high or low. When low, SP0256 uses the internal ROM and when high, SP0256 uses the external ROM. I can see external ROM enabled and data shifted to SP0256, but apparently my data is not correct; still troubleshooting.
I looked at PIC16F13145 data sheet and see it does have 32 LUT which is not enough to implement the logic in current CPLD. However, it may be possible to anticipate what SP0256 is going to do, so the LUT only need to capture the incoming 12-bit addresses then proceed to look up the corresponding data and stuff it to the data shift register which will be clocked out by SP0256. Meanwhile PIC can look up next address and get ready to stuff the data shift register as soon as the 8th data bit is shifted out. So this approach will only use 20 LUT. It may be possible to use PIC16F13145.
Bill
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