EMMU

Description

Chip for bankswitching support for 130XE.

It gets CAS from FREDDIE, the bank select bits from PIA, A14, A15 and the 6502 HALT signal to control which bank of 8 chips CAS goes to. A14 and A15 then go to FREDDIE for the address range of the extra memory bank (or normal address range with no bank switching). The ANTIC/6502 select bits in combination with the 6502 HALT line, control the switching of the PIA bank number bits to A14/A15 and which bank of memory CAS goes to.

Catalogue numbers

CO25953

GAL replacement instructions

Here is VHDL source (7 KB VHD)
Here is report file (6 KB RPT) (contains readable equations :-)
Here is JEDEC file (2 KB JED) for burning into GAL16V8

Author, Christopher Lang adds:

The attached design fully works! Just replace both U34 and U35 in your 130 XE with IC sockets and use the attached jedec file to burn a gal. Make sure pin 12 is tied somewhere either gnd for 130xe comp. or vcc for 800xl comp.

U35 is 74LS95.

Actually I had to flip a bit in the jedec file manually to make pin 13 an input. Since the halt signal is not used the damned vhdl compiler sets all unused OCLM pins in simple mode of the gal to output. Since the halt signal is still supplied to pin 13 this would be a shortcircuit.

If you want to compile this vhdl file and use your own jedec file no probem, just make sure you bend pin 13 out of the IC socket so that it does not get any signal. Back (c) 1998-2004 Jindroush Last modified: Sat Jan 11 13:09:35 2003