RE: 16 bit RAM on 68K system.

[David Williams <davidwilliams@ozemail.com.au>]

Thanks for your response Galen,

The problem with the 68EZ328 that I am using is that is has upper and lower 
write enable signals (UWE* LWE*) and not upper and lower chip enable 
signals. It has a single output enable (OE*) for read operations as it 
always expects 16 bits to be supplied. The core then looks at either the 
upper or lower 8 bits if only an 8 bit read was required. The 16 bit SRAMs 
I have seen require upper and lower byte (UB & LB) enables (ie both read 
and write). So for read operations the OE* signal from processor needs to 
connect to both UB and LB of SRAM and for write operations the UWE* and 
LWE* signals need to connect to the UB and LB of SRAM. This requires some 
glue logic. If your are really interested there is an app note on motorola 
web site for 68EZ328 (see 
http://www.mot.com/SPS/WIRELESS/pdf/APPNOTES/sram_16bit.pdf)

TIA
David Williams


----------
From: 	Galen Seitz[SMTP:galens@northwest.com]
Sent: 	Wednesday, August 18, 1999 11:02 AM
To: 	davidwilliams@ozemail.com.au
Subject: 	Re: 16 bit RAM on 68K system.


What ram were you planning to use?  I just looked at a samsung databook
and their 64Kx16 SRAM has /CS, /UB, and /LB.  This ought to work with the
328 without any glue logic.  The part number is KM616V1000B.  I'm not
necessarily advocating Samsung.  I think you should be able to find several
vendors who make suitable parts.  Cypress, Toshiba, Hitachi, and SMOS
come to mind.

hope this helps,
galen

--
Galen Seitz
galens@alum.mit.edu
hm     503-525-7949
wk     503-617-0808 x109
wk fax 503-617-0809




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