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expand chips tested list in docs

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Tom Nisbet 2022-12-12 18:05:27 -05:00
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docs/prom-families.md
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@ -152,7 +152,7 @@ The 8755 build of TommyPROM also has a circuit to control the 25V programming pu
|:--- |:--- |:--- |:--- |:--- |
|AT28C256 |Atmel, others|EEPROM |28C |Fully supported|
|SST39SF040|Microchip |Flash |SST39SF|All SST39SF0x0 supported|
|WE27E257 |Winbond |EEPROM |27 |Continual 12V or 14V for program/erase|
|WE27C257 |Winbond |EEPROM |27 |Continual 12V or 14V for program/erase|
|AT29C010 |Atmel |Flash |28C |Only with 128 byte or less sector size|
|8755A |Intel |EPROM |8755A |Requires 25V pulses to program|
@ -178,12 +178,15 @@ writing new data. The code keeps track of the current sector and will automatic
an erase operation whenever a write starts to a new sector. The _Erase_ command is
supported, but is not needed unless overwriting new data to a single sector.
#### 27E257
#### 27C257
The Winbond WE27E257 and WE27C257 appear to be identical 32Kx8 EEPROMs. These have a
_VPP_ pin that needs a constant 12V during programming. Unlike the newer 28C EEPROMs,
these chips do not automatically erase before writing to a location. Instead, the
entire chip is erased by applying 14V to _VPP_ and _A9_ and then pulsing _CE_.
The Winbond WE27C257 and WE27E257 appear to be identical 32Kx8 EEPROMs. The 27C version
has been tested.
These EEPROMs have a _VPP_ pin that needs a constant 12V during programming. Unlike the
newer 28C EEPROMs, these chips do not automatically erase before writing to a location.
Instead, the entire chip is erased by applying 14V to _VPP_ and _A9_ and then pulsing
_CE_.
Because the chips use a constant high voltage for programming instead of a pulse, an
external power supply and two diodes can be used to supply either 5V or 12V to the