Re: External Ram on Z8?
- From: Paul Keinanen <keinanen@xxxxxx>
- Date: Sun, 16 Jul 2006 23:53:34 +0300
On Sat, 15 Jul 2006 13:34:47 -0400, ziggy <ziggy@xxxxxxxxxxxxxxxx>
wrote:
Wondering if there is a way to add external ram to a Zilog Z8. It does
not appear that there is from looking the docs and pin-out, but i might
have missed something.
The integration of the Z8 is really nice to reduce parts count, but 4k
ram isnt going to cut it in my case.
Practically any processor with a few general purpose input/output
ports and with some external latches can be used to connect gigabytes
of RAM for _data_ storage. The problem is that for typical DRAM
access, the multiplexed row/column address can be taken from some
output port bits, you then would have to generate the RAS/CAS signals
programmatically through to separate output port pins, thus the access
would be quite slow, but still well within the maximum times allowed
for DRAMs.
For the actual data transfer, when using external RAM with a common
I/O pin, just remember to program the controller port data direction
register as input for a read operation and as output for a memory
write operation.
These methods are usable, if you need a lot of RAM, but the transfer
rate is low.
Executing programs from such external memory would be much more
challenging :-)
Paul
.
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- External Ram on Z8?
- From: ziggy
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