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53 lines
2.7 KiB
Markdown
53 lines
2.7 KiB
Markdown
---
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title: Adding Chip Families
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has_children: false
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nav_order: 5
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---
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# Extending the design to new chip families
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## Hardware
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There are currently two hardware flavors - one for 28C series EEPROMs and one specifically
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for the Intel 8255A UV EPROM. There is also a work-in-progress version for 27C series
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chips.
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The 8755A chip uses a multiplexed set of address and data lines that are directly driven
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by the Arduino. Most other chips will not use this addressing method. The 8755A design
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also includes a circuit to switch the programming voltage under software control. This
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may be useful for other chips that use non-5V programming voltages, although many of these
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chips, like the 27 series EPROMS, have a programming voltage that remains on for the
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entire write and verify cycle. For those chips, it may be easier to simply switch the
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programming voltage manually for these chips.
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The basic hardware design, used for the 28C EEPROMs, is much more adaptable to additional
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chip families. This design uses two shift registers to create 16 dedicated address lines
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from only 3 Arduino pins. This design, plus manual switching of the program voltage, would
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be very adaptable to EPROMs like the 2716, 2764, 27040, and 272001. The hardware has
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already been used with these chips for read-only operations.
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The current design can directly address chips as large as 512K bytes, like the 29C040.
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Use the shift registers for A0..A15 and wire Arduino pins D10..D12 to A16..A18 on the
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target chip.
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# Software
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The software design is modular, allowing easy extension for chips with different
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programming algorithms. A new class can be added for each new chip family. This class
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will include code for byte reads, byte writes, and optional block writes if the chip
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supports it. All of the chip-specific code will be in this single class.
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The basic steps to support a new chip are as follows:
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* Create or copy an existing PromDeviceXX class to create a new .cpp and .h file for the
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chip-specific code.
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* Define the pin assignments and implement the chip-specific setAddress, readByte, and
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burnByte code in the new files. The setAddress code can call the PromAddressDriver code if
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the shift register address hardware is used.
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* If supported, also add chip-specific burnBlock code.
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* Be sure that the new files have unique #if defined code that matches the class name.
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* Edit Configure.h to add the conditional code includes the new PromDevice subclass.
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* Edit TommyPROM.ino to add the conditional code that declares the new device.
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Note that after files are added or renamed in the TommyPROM directory, the project needs
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to be reopened in Arduino IDE to get the changes.
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