Static RAM chip source (& S-100 related questions...)
ajp166 at verizon.net
Sun Aug 15 15:58:19 CDT 2010
On 08/15/2010 03:02 PM, Chuck Guzis wrote:
> On 15 Aug 2010 at 10:12, Glen Slick wrote:
>> One other thing that might help the situation is that the 2147 enters
>> an automatic power-down mode when the CE# input is at a high level.
>> For example the datasheet for the CY2147-35 says the max operating
>> current is 125ma while the max standby current is 25ma.
>> Do MM5257 parts enter a standby mode when not selected? I don't have
>> a datasheet handy. Which would draw more current total, two banks of
>> MM5257 parts, or two banks of CY2147 parts where at least one of the
>> two banks should be in standby mode?
> If the 5257 parts are like the TMS4044 parts, standy is entered by
> reducing Vcc to 2.4V. Otherwise, maximum operating power dissipation
> is given as 303 mW. I somehow doubt that the memory board in
> question has the smarts to drop Vcc.
> There also exist CMOS versions of the same chip--the Motorola
> MCM146504, the Harris HM6504 or the Intersil IM6504 is one such, with
> a standby power of 10mW. These are the same speed (450nsec) as the
> TMS4044s. So more grist for your mill...
Some parts like the 6504 are not fully static and the
logic is somewhat dynamic with the transition of CS
performing the precharge of the gating logic around a
static cell. That means you must cycle CS for every
address change withing a read/write or RMW cycle.
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