RCA COSMAC Operator's Manual page 56

CUSTOM MEMORY MODULES (cont'd)
ADDRESS AO -A II
(12)
4K
RAM
DATA IN
(8)
MEMORY
WRITE
DATA' OUT
(8)
SELECT
A I 2 - P - - - -.....
DESELIK- P
(PI-X)
RMDS-P
-------..----..&
fig.IS: Custom 4K RAM Functional Diagram
The solution above mlnlmlzes the logic and wiring at the
expense of generality. A second 4K RAM identical to the
above could not be added to the system as it stands. A
more general-sD1ution requires central block selection
logic (decoding of address bits 12-15). Then it would be
possible to design larger capacity memory modules which
can be moved in address space by backplane wiring changes,
in a manner similar to that discussed for the S12-byte
banks supplied with the Microkit.
- so -