adapter schematic + others
fixed resistor R1 is better to use trimmer variable resistor of 2-2.5KB
- so can adjust timings better. Monostable delay should be around
180 nS. But it depends from used GAL delays and CF card too.
If want to connect 2 CF cards need 2 CF sockets. In that
case pin 39 of Slave socket must be left unconnected. Instead CF socket
may use IDE connector + IDE-CF adapter. Connections should be obvious
: then no A03-A10, /ATASEL, /CSEL, /WE, /VS1 . /REG is
on IDE & /INPACK is DMARQ on IDE . Possible problem:
some IDE-CF adapters have unconnected DMA lines - in that case (of
course) fast DMA transfer will not work !
IMP DMA chip in Mega ST : On chip is printed:
© ATARI 1987
9022 PAF or 885 1DKA ( year 90 or
88 ) .
With such chips I observed problems only in Mega ST - unreliable
work, even in slow mode. In 1040 ST it worked well. Is problem in bad
cowork with blitter (what is not present in 1040) or not, I can not
say. In any case, replacing IMP DMA with 'regular' one solves problems.
As regular DMA chip I consider: CO25913-38 .
Decoupling ceramic capacitors (100-220nF) on all chips are
on GAL - best to solder on top of it.
If adapter is connected to ST, and no card inserted it will block
floppy controller - so remove adapter in such case. Same is when no
Master, just Slave inserted.
GAL logic (GAL+JED files)
PP, Sept. 2010. June 2011