more one chip RAMCAL

[jsg at donet.com]

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I've spent a day or two looking at the 730 board. I see two ways of
doing the battery backed up RAM (DS1230Y) RAMCAL. A one chip version
of RAMCAL for about $11.00 for the 730 board only.

first.... there are four unpopulated chips on the board (U3 NAND gate,
U4 3:8 de-mux, and U8 ram) that can add 2k of RAM to the memory map.
These chips can be used to generate all the RAM control signals.

The two ways I see of adding RAMCAL are... (subject to refinement...)

(1) insert the RAM chip into the MEMCAL and add U8 the nand gate. use
the "unused" 4-5-6 nand gate to generate A15!; jumper to CS! on memcal
socket (leave 10k to gnd). connect from the cpu board to the MEMCAL
OE! (U8:3) and WE!  (U8:8). Finally, rewire, on the memcal, A14 to the
correct pin on the RAM chip.

(2) Standoff a larger (28 pin) socket at U3 on the cpu board. add U8
the nand gate and again use the 4-5-6 gate for A15!. Jumper A11-A14 to 
the socket and correct pin 24 (vcc->A13). The MEMCAL EEPROM can be
disabled by tying CS! high on the back oon the cpu board.

john gwynne