20 Oct
2010
20 Oct
'10
5:48 p.m.
On 10/20/2010 02:15 PM, Ethan Dicks wrote:
Could you use a 4164 instead? (it might require a
pull-up or
pull-down on pin 9 so it doesn't float).
I'd just hardwire pin 9 to either
+5V or ground. Probably easiest to
tie it to +5V on pin 8.
16K DRAMs all required 128 row refresh in 2 ms.
64K DRAMs came in two kinds. Some required 256 row refresh in 4 ms,
while others (specifically intended for compatibility with 16K DRAMs)
required only 128 row refresh in 2 ms. The latter kind will work with a
7-bit refresh counter (e.g., 3242, or the counter built into the Z-80),
while the former will not.
However, in this case, you're only going to use 128 rows (and only half
of each row), so either kind of 64K DRAM should be suitable.
Eric