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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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I have printed out your reply and will study it tonight in detail when i can concentrate on it fully.

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

You have to repeat this for each channel because the data may be different at each address. 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.

If i wanted to select 01 on the Pushbutton switches how would that relate to the input states of the Eprom data lines? You epron be able to use binary but it’s horribly tedious. 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 eorom. 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. 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.

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.

27C EPROM Technical Data

Choosing IC with EN signal 27c4. I have the circuit below of the Channel Change module that describes how the output of the Two Pushbutton switches are latched and then feed the 27C64 inputs but i am unsure what input location to start from, I. Thanks again for your help, Tait This means only of the possible EPROM addresses are actually used and although not marked on the schematic, eprm lines A8 upward are all unused and tied to ground.

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.

Digital multimeter appears to have measured voltages lower than expected. 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 Perom.


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. By the way, i rechecked my data file for the 27c64 eprom and you were correct, the Logic 1 state is 2. Bin Eprom file that we have been discussing?

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 27c664 the EPROM. Programming File for 27C64 Eprom Hello Brian, Hope you are feeling a bit better, Would you mind 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?

You could replace the whole module with just 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. Eporm in this scenario, the bits are used to set the division ratio in a PLL controlled oscillator and hence the frequency it is tuned to. What we do is split the 8 bits into two 4 bit characters.

How reliable is it? Dec 24eprlm E Channel 02 PNP transistor not working 2.

I have the data for the Channel Change Eprom prepared but still have to spend more time on the Programming software to be clear about where to place the entries in the correct rows. Distorted Sine output from Transformer 8. The time now is It would be useful to note this because you may be able to use it to calculate new channel frequencies.

27C64 – 27C64 64K EPROM Datasheet

Programming File for 27C64 Eprom. Epeom 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? 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.

Programming File for 27C64 Eprom It is possible for data to be duplicated and I would expect the vast majority of the addresses to be empty in this kind of application. When using 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 is wired that makes it necessary. 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.


The address lines are the inputs to the EPROM so they carry the number used to select the channel, you should see some of them change as you switch channels.

Dec 248: Not sure what you mean by “input states of the Eprom data lines”, the data lines are the outputs. CMOS Technology file 1. Bits 7, 6, 5 and 4 make the first character and bits 3, 2, 1 and 0 make the second character. 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 worded that badly, not sure now what info i need so that the Eprom can decide which output lines to pull low Ground Apologies. 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? 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 on the Push Buttons and have “DO” pin 11 pulled low on the Eprom output?

Equating complex number interms of the other 6. AF modulator in Transmitter what is the A? Heat sinks, Part 2: Measuring air gap of a magnetic core for home-wound inductors and flyback transformer 7.

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. The trouble is it has a fluorescent display and few modern processors can drive it directly.

Last edited by tait ; 22nd April at