Re: Ultimax questions

From: Segher Boessenkool <>
Date: Thu, 10 May 2012 20:32:36 +0200
Message-Id: <>
>> It looks like the binary dump in the latter file is formatted  
>> differently. When you strip the address and trailing * and wrap  
>> the lines at 32 instead of 40 bits per line, it starts to look  
>> more like the earlier dump.
> Yes, except it is complete ;-)
> They are not identical; I'll have a look what the difference is.
> Interesting.

It turns out that all bit pairs in the AND array are swapped
between the two JED files.  They are identical otherwise (ignoring
the missing lines).  I suppose one of the JED file programs has
a bug, or alternatively one of the devices inverts all its inputs.

The JED bitstream is 48 lines of 40 bits, and a final 8 bits.
Each line is 16 pairs of inputs for the AND array, creating a
minterm; and then 8 bits for the OR array, saying which sum terms
use that minterm.  The final 8 bits are to optionally invert the

The inputs are (pin #, pin name, c64 pin name, where does the
signal come from):

  9 I0   #CAS     (VIC)
  8 I1   #LORAM   (CPU P0)
  7 I2   #HIRAM   (CPU P1)
  6 I3   #CHAREN  (CPU P2)
  5 I4   #VA14    (CIA2 PA0)
  4 I5   A15      (CPU)
  3 I6   A14      (CPU)
  2 I7   A13      (CPU)
27 I8   A12      (CPU)
26 I9   BA       (VIC)
25 I10  #AEC     (VIC)
24 I11  R/#W     (CPU)
23 I12  #EXROM   (cartridge)
22 I13  #GAME    (cartridge)
21 I14  VA13     (VIC A5/A13)
20 I15  VA12     (VIC A4/A12)

and the outputs are

18 F0   #CASRAM  (#CAS on RAM)
17 F1   #BASIC   (basic rom #CS)   a000..bfff
16 F2   #KERNAL  (kernal rom #CS)  e000..ffff
15 F3   #CHAROM  (char rom #CS)    d000..dfff
13 F4   GR/#W    (colour RAM #WE)  d800..dbff
12 F5   #IO      (I/O #CS)         d000..dfff
11 F6   #ROML    (cartridge #CS)   8000..9fff
10 F7   #ROMH    (cartridge #CS)   e000..ffff

All the equations in pla.txt are correct as far as I can see.

There are two minterms computed that aren't used:
	ras, addr 1101, cpu write

My guess is that those were used on some earlier revision and
never removed.  The first is right before the I/O minterms, the
other before the CASRAM minterms.


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Received on 2012-05-10 19:00:36

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