Topics

MCM68766 and MCM68764


 

Looking at the datasheets these devices appear the be the same, am I missing
something, or was it just a case of the MCM68766 superseding the MCM68764?

Thanks
David


 

On Fri, Jun 5, 2020 at 10:08 AM, David C. Partridge wrote:


Looking at the datasheets these devices appear the be the same, am I missing
something, or was it just a case of the MCM68766 superseding the MCM68764?
AFAIR the two are mostly the same. The main/only difference is in the Enable lines. The 68764 has a Chip Enable(low) ('CE) line, which in the 68766 is an Output Enable(low) ('OE) line.
Data availability in the 68766 after 'OE is faster (100 ns) than in the 68764 after 'CE (450ns). OTOH, the ('CE) in the 68764, when high (i.e. Disabled), puts the chip in a low-power mode.
Raw read access time for both chips is the same (450ns) and 'CE is as fast as the delay from Address Valid to Data Valid with 'CE asserted. (Nominal max. times for the most popular versions).
If the low power capability of the 68764 is irrelevant, a 68766 will always do, the 68764 may not. I haven't checked if the 68764 will fulfill the 7854's timing requirements.

Raymond


 

That makes sense - also explains why my rommer that "supposedly" doesn’t support MCM68766 is quite happy when told they are MCM68764!

David

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Raymond Domp Frank
Sent: 05 June 2020 12:40
To: TekScopes@groups.io
Subject: Re: [TekScopes] MCM68766 and MCM68764

On Fri, Jun 5, 2020 at 10:08 AM, David C. Partridge wrote:


Looking at the datasheets these devices appear the be the same, am I missing
something, or was it just a case of the MCM68766 superseding the MCM68764?
AFAIR the two are mostly the same. The main/only difference is in the Enable lines. The 68764 has a Chip Enable(low) ('CE) line, which in the 68766 is an Output Enable(low) ('OE) line.
Data availability in the 68766 after 'OE is faster (100 ns) than in the 68764 after 'CE (450ns). OTOH, the ('CE) in the 68764, when high (i.e. Disabled), puts the chip in a low-power mode.
Raw read access time for both chips is the same (450ns) and 'CE is as fast as the delay from Address Valid to Data Valid with 'CE asserted. (Nominal max. times for the most popular versions).
If the low power capability of the 68764 is irrelevant, a 68766 will always do, the 68764 may not. I haven't checked if the 68764 will fulfill the 7854's timing requirements.

Raymond


 

Hi David,

Anything that will increase the number of eyeballs looking at the datasheets
will improve the chances of finding the answer.
More people will be willing to help if you make it easier to do.
Providing links to the exact datasheets you found would save any of us
willing to compare them a lot of work looking for them.
It's important to know exactly where you got each datasheet so we are
looking at the same ones you are.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C.
Partridge
Sent: Friday, June 05, 2020 1:09 AM
To: TekScopes <Tekscopes@groups.io>
Subject: [TekScopes] MCM68766 and MCM68764

Looking at the datasheets these devices appear the be the same, am I missing
something, or was it just a case of the MCM68766 superseding the MCM68764?

Thanks
David






--
Dennis Tillman W7pF
TekScopes Moderator