2708 Programming Algorithm?

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Tue May 7 11:40:51 2002

>From: ard_at_p850ug1.demon.co.uk
>
>>
>> Hi
>> I believe the main difference between the 2708 and 8708 is that
>> the 8708 could handle negative levels on the data bus so it
>> could be connected directly to the 8080's data bus.
>
>Err, Every 8080 I've ever used has had TTL levels on all the pins apart
>from the clock inputs. There is no problem using 'normal' EPROMs with an
>8080 AFAIK
>
>-tony
>

Hi
 I couldn't remember exactly what it was so I looked it up.
I was both right and wrong. First, it wasn't negative levels,
it was positive levels. The 8080 requires 3.3 volt highs on
their inputs. Most TTL only require 2.5 volts. Intel made a
number of parts compatable with these higher input threshold
levels. The statement that 8080's are TTL compatable is
only mostly true. They could drive TTL but to receive from
TTL often required pull-up resistors or drivers that had
higher outputs. So, it was drive level and not input voltage
that was significant.
Dwight
Received on Tue May 07 2002 - 11:40:51 BST