mirror of
https://github.com/TomNisbet/TommyPROM.git
synced 2024-11-24 08:31:16 +00:00
51 lines
2.7 KiB
Markdown
51 lines
2.7 KiB
Markdown
---
|
|
title: "Adding New Chip Families"
|
|
permalink: /docs/extending
|
|
exerpt: "Extending TommyPROM to support new EEPROM, EPROM, and Flash chip families"
|
|
---
|
|
|
|
## Hardware
|
|
|
|
There are currently two hardware flavors - one for 28C series EEPROMs and one specifically
|
|
for the Intel 8255A UV EPROM. There is also a work-in-progress version for 27C series
|
|
chips.
|
|
|
|
The 8755A chip uses a multiplexed set of address and data lines that are directly driven
|
|
by the Arduino. Most other chips will not use this addressing method. The 8755A design
|
|
also includes a circuit to switch the programming voltage under software control. This
|
|
may be useful for other chips that use non-5V programming voltages, although many of these
|
|
chips, like the 27 series EPROMS, have a programming voltage that remains on for the
|
|
entire write and verify cycle. It may be easier to simply switch the programming voltage
|
|
manually for these chips.
|
|
|
|
The basic hardware design, used for the 28C EEPROMs, is much more adaptable to additional
|
|
chip families. This design uses two shift registers to create 16 dedicated address lines
|
|
from only 3 Arduino pins. This design, plus manual switching of the program voltage, would
|
|
be very adaptable to EPROMs like the 2716, 2764, 27040, and 272001. The hardware has
|
|
already been used with these chips for read-only operations.
|
|
|
|
The current design can directly address chips as large as 512K bytes, like the 29C040. Use
|
|
the shift registers for A<sub>0</sub>..A<sub>15</sub> and wire Arduino pins D10..D12 to
|
|
A<sub>16</sub>..A<sub>18</sub> on the target chip.
|
|
|
|
# Software
|
|
|
|
The software design is modular, allowing easy extension for chips with different
|
|
programming algorithms. A new class can be added for each new chip family. This class
|
|
will include code for byte reads, byte writes, and optional block writes if the chip
|
|
supports it. All of the chip-specific code will be in this single class.
|
|
|
|
The basic steps to support a new chip are as follows:
|
|
* Create or copy an existing PromDeviceXX class to create a new .cpp and .h file for the
|
|
chip-specific code.
|
|
* Define the pin assignments and implement the chip-specific setAddress, readByte, and
|
|
burnByte code in the new files. The setAddress code can call the PromAddressDriver code if
|
|
the shift register address hardware is used.
|
|
* If supported, also add chip-specific burnBlock code.
|
|
* Be sure that the new files have unique #if defined code that matches the class name.
|
|
* Edit Configure.h to add the conditional code includes the new PromDevice subclass.
|
|
* Edit TommyPROM.ino to add the conditional code that declares the new device.
|
|
|
|
Note that after files are added or renamed in the TommyPROM directory, the project needs
|
|
to be reopened in Arduino IDE to get the changes.
|