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HC573A bost address and data to eprom 27c256

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sandofsad

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Hi, i'm stuck on this problem. i try to boost data and adress from controller board to an eprom 27c256. From the controller board it signal, data and address will be boost using HC573A latch ic.

aaa.JPG


here the theory i try to solder up the component. All address input and address data from eprom 27c256 will be connected to HC573A input. And all HC573A output will go to eprom same pin and sequence from controller board. But HC573A OE pin 1 and LE pin 11 here should i connect?
 

betwixt

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For the address HC573 ICs, tie the LE pins high and the OE pins low, this will make the latch transparent so it acts like a signal buffer.

For the data HC573 IC, tie LE high and connect OE to pin 20 of the socket. The 'D' inputs go to the EPROM and the 'Q' pins go to the socket, remember you send addresses to the EPROM but you read data from it so the buffer has to be the other way around to the address signals. You can either tie pin 20 of the EPROM to ground or to pin 20 of the socket, it will work the same either way.

Brian.
 

sandofsad

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For the address HC573 ICs, tie the LE pins high and the OE pins low, this will make the latch transparent so it acts like a signal buffer.

For the data HC573 IC, tie LE high and connect OE to pin 20 of the socket. The 'D' inputs go to the EPROM and the 'Q' pins go to the socket, remember you send addresses to the EPROM but you read data from it so the buffer has to be the other way around to the address signals. You can either tie pin 20 of the EPROM to ground or to pin 20 of the socket, it will work the same either way.

Brian.
Wow thanks Brian, it detail and easy for understand with your explanation, now i try to make sample pcb board and try the step you given. i will post the result here. thanks :grin:
 

sandofsad

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View attachment 58522

Hi, i failed to make it work properly, as the attachment i wire up and test, it cannot read and the 27C256 EPROM, i used about 2 feet wire from controller socket to HC573A board.. This project to boost up address and data from Honda ECU obd1 that using 27c256 EPROM. can you check my circuit is there any wrong about the connection..

Looking to the some manufactured board, is used some capacitor and other ic in the HC573A 27C256 booster board.

Chip Extender Remote.jpg
 

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It's difficult to see from the photograph but it appears you have one of the ICs backwards.
Are you sure the HC573 carrying the EPROM data lines is wired [EPROM D] -> [HC573 D ---- Q] -> [Socket] ?
For example EPROM pin 11 to HC573 pin 2, HC573 pin 19 to socket pin 11.
From the photograph it looks like all the buffers are passing signals TO the EPROM, the data one should be reading FROM it.

Brian.
 

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