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expand chips tested list in docs

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Tom Nisbet 2022-12-12 18:02:26 -05:00
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docs/prom-families.md
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@ -90,7 +90,7 @@ to that sector.
## Misc Flash ## Misc Flash
**29C Series** #### 29C Series
The 29C series flash chips are similar to the 28C EEPROMs, except they must erase an The 29C series flash chips are similar to the 28C EEPROMs, except they must erase an
entire sector before programming new data. The start of a block write operation causes entire sector before programming new data. The start of a block write operation causes
@ -110,7 +110,7 @@ of the sector. The second write will then erase the data just written and then
bytes into the second half of the sector. To fix this, the code would need to be modified bytes into the second half of the sector. To fix this, the code would need to be modified
to keep 256 bytes of data from two packets before initiating a block write. to keep 256 bytes of data from two packets before initiating a block write.
**28F Series** #### 28F Series
The 28F series flash do not have sectors. The entire chip must be erased before writing The 28F series flash do not have sectors. The entire chip must be erased before writing
new data. Data is written a byte at a time using a command register to control the new data. Data is written a byte at a time using a command register to control the
@ -119,7 +119,7 @@ the programming or erase operations**. TommyPROM does not currently support 28F
but it would not be difficult to write a driver. The default 28C driver will read 28F but it would not be difficult to write a driver. The default 28C driver will read 28F
chips. chips.
**29F Series** #### 29F Series
The 29F series flash have sectors that must be explicitly erased before writing new The 29F series flash have sectors that must be explicitly erased before writing new
data. Data is written a byte at a time using a command register to control the data. Data is written a byte at a time using a command register to control the
@ -150,8 +150,55 @@ The 8755 build of TommyPROM also has a circuit to control the 25V programming pu
|Model |Manufacturer |Type |Module |Notes| |Model |Manufacturer |Type |Module |Notes|
|:--- |:--- |:--- |:--- |:--- | |:--- |:--- |:--- |:--- |:--- |
|28C256 |Atmel, others|EEPROM |28C |Fully supported| |AT28C256 |Atmel, others|EEPROM |28C |Fully supported|
|SST39SF040|Microchip |Flash |SST39SF|All SST39SF0x0 supported| |SST39SF040|Microchip |Flash |SST39SF|All SST39SF0x0 supported|
|27E257 | |EEPROM |27 |Continual 12V or 14V for program/erase| |WE27E257 |Winbond |EEPROM |27 |Continual 12V or 14V for program/erase|
|29C010 | |Flash |28C |Only with 128 byte or less sector size| |AT29C010 |Atmel |Flash |28C |Only with 128 byte or less sector size|
|8755A |Intel |EPROM |8755A |Requires 25V pulses to program| |8755A |Intel |EPROM |8755A |Requires 25V pulses to program|
#### 28C256
Tested with chips from several manufacturers including Atmel AT28C256, Xicor X28C256, and
CSI CAT28C256. Also works with the smaller 28C64 and 28C16 chips, although some
parameters may need to be adjusted. Some smaller chips do not support SDP, so the _Lock_
and _Unlock_ commands have no effect. Check the datasheet to see if block writes are
supported. Some 28C16s use a 16 byte block instead of the 64 bytes used on the 28C256.
It is always safe to just set the block size parameter to zero when declaring the chip to
disable block writes altogether.
The 28C chips do not need to be explicitly erased. Each memory cell is automatically
erased during a write operation, so they are more similar to a slow RAM than to other
PROMs.
#### SST39SF040
The SST39SF driver supports all chips in this family, so the 040, 020, and 010 chips can
be all be used with no code change. These chips use sectors that must be erased before
writing new data. The code keeps track of the current sector and will automatically do
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
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_.
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
pins for programming and erasing.
Note that the WE27x257 chip are almost a drop-in replacement for the 28C256. The _WE_,
_VPP_, and _A14_ pins are the only differences. For reading, the _VPP_ pin should be
connected to 5V.
#### 29C010
The 29C0x0 chips are 5V sectored flash chips. They automatically erase a sector at the
start of a new write, so they can be used with the default 28C code.
Note that some versions of the 29C040 use a 256 byte sector size. This will not work
with the TommyPROM code because the XModem transfer buffer is only 128 bytes. Code
changes would be needed to buffer up two packets of data into a single write operation
for chips with the 256 byte buffer.