The Microchip Technology Inc. 27C64 is a CMOS 64K bit (electrically) Programmable Read Only Memory. The device is organized as 8K words. 27C64 64k (8k X 8) CMOS EPROM FEATURES. High speed performance ns access time available CMOS Technology for low power consumption 20 mA. 27C64 EPROM Datasheet, 27C64 64K EPROM Datasheet, buy 27C

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Results 1 to 20 of Programming File for 27C64 Eprom. Programming File for 27C64 Eprom Hello, Was wondering if someone that has had some experience in creating a BIN or HEX file suitable for a 27C64 Eprom could point me in the right direction re creating a file that would allow the above Eprom to control the output of its data lines D0 – D7 so that it will switch the lines either high or Low i. The device is a Remote Channel Change module for a Repeater rack and allows remote selection of channels in the TX and Rx modules by pulling various data lines in the same chip installed in the modules either high or low depending on the channel selected.

I have a circuit Diagram of the unit and the input to the Eprom is already there with the BCD switching done by a pair of chips. I have the Eproms for the TX and RX modules correctly burned with programming files provided by the equipment manufacturer Tait but i am lost as to how to create a BIN or Hex file from scratch to get the Channel Change Eprom to output the correct switching via its Data out lines.

Apologies for the long first post but if anyone could point me the right direction as to how to create this file i would be most grateful before i wear out my UV Eraser or the Spare Eproms i have been using to test the files Regards. If I understand what you want, you have known input lines states and you want to convert them to different output line states by using the EPROM as a look-up table. It’s fairly easy to do, first draw a table on graph paper or use a spreadsheet of the input states, these are the EPROM address lines.

Then for each input state, write the output state you need, this is what the EPROM should produce on it’s data lines. You might be able to use binary but it’s horribly tedious.

Remember the 27C64 has 13 address lines so the values on them can be from to 1FFF but the output is 8 bits so can only go from 00 to FF. For example if the input lines were the address is C and you wanted to output on the data lines the value to place in C would be 9B. When you have done it for all the input combinations you need, program the chip. It’s better to share your questions and answers on Edaboard so we can all benefit from each others experiences. This is exactly what is required, the Thumbwheel switches generate the line states from a Numerical setting 01,02,- 99, etc and the module displays these on the 7 seg Leds and switches the output lines to match, controlling the Radio Modules.

You have cleared up a lot of my confusion over this and have given me a Good place to start, time to do some serious study. Programming File for 27C64 Eprom Thanks Brian, I am still having trouble getting a Correct Eprom image that will work correctly combining the Channel change module and the radio Module.

The radio module Eprom is working correctly as i can manually select the Channels via the 8 pin Dip switch and they follow the Dip Switch codes from the manual.

I am not fluent with Eprom programming and i have probably messed up the conversion from Binary to hex or placed it in the wrong location. I have the circuit below of the Channel Change module that describes how the output of the Two Pushbutton epeom are latched and then feed the 27C64 inputs but i am fprom what input location to start from, I. If i wanted to select 01 on the Pushbutton switches how would that relate to the input states of the Eprom data lines?

I would be very grateful for any further assistance you might be able to provide on the above. Not sure what you mean by “input states of the Eprom data lines”, the data lines are the outputs. I will try and scan a copy of the Circuit Diagram from a hard copy i have. I worded that badly, not sure now what info i need so that the Eprom can decide which output lines to pull low Ground Apologies.

Last edited by tait ; 21st April at Programming File for 27C64 Eprom Got them thanks. The on the third schematic is periodicaly pulsing the latch signal so the switches are read in. The CD can only decode decimal numbers so I’m guessing the range you can select is from 00 to 99 and is BCD coded.

This means only of the possible EPROM addresses are actually used and although not marked on the schematic, address lines A8 upward are all unused and tied to ground. I assume the outputs from the EPROM are connected to the inputs of a PLL circuit so that different frequencies are selected for each combination of 27c6 state.


It that is the case, and if the radio is working at the moment, I suggest you note the voltages on the EPROM outputs for each channel number you select.

It would be useful to note this because you may be able to use it to calculate new channel frequencies. This makes it easy, you can directly use the channel number as the EPROM address and at that address put the binary number of the output you want. There will be gaps in the contents of the EPROM so don’t worry if there are empty addresses you don’t use. The “External Interface” on the left Hand top is where the Channel Change eprom output connects to directly and you can manually select any of the channels that have been previously programmed via the Tait 227c64 into the radio’s own Eprom, 227c64 the 8 DIP switches.

27C64 – 27C64 64K EPROM Datasheet

E Channel 02 Thanks for clearing up the mystery of the Address lines, i have a Hex editor attached to the Eprom Programming software that allows me to enter data at specific locations so hopefully i am on the right track now. I don’t mean to take up all of your time but i would be really interested in hearing more about the microprocessor option if you are able, there is plenty of space on the channel change module and might be easier to generate a small board that could plug in in place of the Eprom.

Thanks again for your help, Regards. Last edited by tait ; 22nd April at Programming File for 27C64 Eprom It’s a strange system, if if the date is difficult to read it was well into the era of microprocessors so using so much discrete logic seems a bit backwards. What I meant by using a small micro was you can achieve the same result as using a ‘hardware’ EPROM look-up table by doing it in software.

You could replace the whole module with 27c644 a handful of modern components, in fact you could replace the entire selector AND channel EPROM board with a simple micro and a display driver circuit. The problem is knowing where to stop, not where to start!

I have a rather old but still functional FRG receiver here which is crying out for a revised processor board, especially as the original has some serious bugs in it’s software. The trouble is it has a fluorescent display and few modern processors can drive it directly.

It would have to be replaced with an LCD but that introduces mechanical problems of fitting one in the same space. Programming File for 27C64 Eprom Thanks Brian, Looks as though i might have to stick with e;rom Eprom Idea for a bit longer, i have a few spare 27c64 available that i think are perom good.

27C64 Datasheet pdf – 64K (8K x 8) CMOS EPROM – Microchip

I have attached a small portion of the instructions that were included in the manual regarding the odd way the data is entered to complete the Eprom. Would it be possible for you to take a quick look and tell me where, looking at the diagram i would enter the data to have “01” selected eeprom the Push Buttons and have “DO” pin 11 pulled low on the Eprom output?

I have 10 channels but if you could possibly show me this one example i can work the rest out by trial and error, hopefully. Thanks again for your help, Tait Programming File for 27C64 Eprom Sorry for the late reply eprok I’ve had a minor accident and can’t sit upright at the moment!

It makes reading and writing a bit difficult. I’ll respond as soon as I can. Programming File for 27C64 Eprom I’m back again – sorry for the delay, I’ve suffered from a spine problem for years, it causes unpredictable spasms that probably look quite comical to watch but having slipped and torn a muscle in my lower back the last thing I wanted was any sudden movements!

I’m more or less upright again now so “on with the work! What you ask for is very easy to do, you need to think in hexadecimal though instead of decimal.

Because of the strange way the EPROM address pins are connected, the input digits are reversed so if you want channel 10 you use address 01 instead. It is very easy to convert the bit pattern from binary to hexadecimal. What we do is split the 8 bits into two 4 bit characters.

Bits 7, 6, 5 and 4 make the first character and bits 3, 2, 1 and 0 make the second character. Each of the 4 bit patterns is translated to a single hexadecimal character like this: For example, if you wanted EPROM channel 10 to produce an output of you would first reverse the channel digits and use address 01, then split the 8 bit output you want into two becomes then convert each to hexadecimal to find the number to store in the EPROM.


When eproom an EPROM normal use you wouldn’t swap the input digits, you keep them as they are, it’s just the odd way the Tait unit erom wired that makes it necessary.

I wouldn’t be too concerned about what other people find amusing, seeking Humour in other peoples misfortune normally indicates a low self image problem. Glad you are feeling a bit more comfortable, i have hurt my back before and i know just what it feels like.

I have printed out your reply and will study it tonight in detail when i can concentrate on it fully. Will be in touch when i have had a good look with my thinking cap on.

Thanks again for your time, Regards, Chris S. Programming File for 27C64 Eprom Hello Brian, Eorom you are feeling a bit better, Would you epprom having a quick look at the attached Circuit diagram of the other end of this Combination and tell me if i can do a check of which Data output lines coming out of the Channel change module are either “High” or “Low” depending on which Channel is selected?

What i would like to do is check that the unit is sending the correct signals via the Data lines to switch the Eprom on the Radio Channel Board to select the correct channel.

If this is true would i be able to measure with a DVM on DC volts the output state of the data lines out of the Channel Change eprom to confirm i have the correct lines either high or low to replicate the Dip switch settings on the Radio Eprom Board? I have the data for the Channel Change Eprom prepared but still have to spend more time on the Programming software 276c4 be clear about where to place the entries in the correct rows.

Programming File for 27C64 Eprom It’s a static design, meaning there are no signal which change over time unless it’s because you change channel so yes you can use a DVM to check the logic levels.


I’m suspicious of the maximum voltage for logic 1 being 2. In other words anything higher than erpom. There will be a “no mans land” zone at and possibly around 27v64 2. You will see distinctly different voltages on the pins and they will almost certainly be very close to 0V or 5V. The address lines are the inputs to the EPROM so they carry the number used to select the channel, you should 27v64 some of them change as you switch channels.

Measure the voltages on all the Address lines and write down whether they are high or low as a binary number, for example: You have to repeat this for each channel because the data may be different at each address. After a while, when you have got eptom to thinking in hexadecimal it all falls into place, it’s easier than it looks. You can always tell a programmer by the way they count on their fingers then take their shoes off to count on their toes as well!

BTW – my back is much better thanks.

Would you have a minute to take a look at a epro, i have produced in regards this. Bin Eprom file that we have been discussing? This eprim gives me a set of ascending Location Eprlm for the data and and what looks like descending data to go in those locations. Elrom don’t know if this is 27c644 and would be very grateful if you could point out any mistakes in my file as it does not look like any.

Bin files i have seen before. I am using “Eprom45” buffer to generate the. Bin file itself as this is what i use to burn the Eproms but will wait to see if you think this will work the way it should before i attempt to complete the file. After i asked you about using the DVM to check whether the output lines were at the correct Logic level i suddenly remembered i had a Logic Probe from when i was at tech, this is powered from its own Batt supply but do i have to tap into the Neg Supply on the circuit to get a ground signal for the probe to work?

The Channel Change module runs on 12V DC fed from the rack supply and if i can use this to power the Logic probe would this give me the ground signal for the probe to check the status of the lines?

Thanks for your Help, Brian. Programming File for 27C64 Eprom Without intimate knowledge of the radio I can’t say the epom are correct but they certainly look realistic. I would guess the data ends up in a PLL circuit elsewhere in the radio so the equal sized jumps in EPROM data would suggest that the same frequency spacing exists between each channel 10Khz, 25KHz or whatever.