(copy of discussion between Dave & myself, just to complete the picture)

"Hi Dave,

I think you'll have a problem, just counting pulses (clock &/or data), as the reader is an insert type & you can never be sure if the card always goes in to the same point.
I've just remembered* that I've done a project like this a few years ago (*I think I'm getting Oldtimer's Disease!). It was for a bank head office, where they wanted to restrict access to one of the rooms, based on the existing access & time management cards. The good news was that the employee number was in the first few characters on the card. The bad news was that the card was read with the stripe below on the left (normal ISO is below at right). More good news - the reader can be re-built (ah! those Japanese!).

When I get home, I'll send you a copy of the code (8085 assembler) - it should arrive at breakfast time (Friday is a short day for us here). You just need 3 inputs : card in, clock & data. There is no speed problem, of course; an insertion at 10cm/sec gives a clock frequency of only 300Hz!

Yet another project I worked on (in 1983?*) also used insert readers, but with a USART (Intel 8251) to do all the hard work : you set the chip to work in sync mode, 5 bits/character, odd parity, you get the comms clock from the card reader clock, your sync byte = the 1st character on the stripe, which should be B hex; for every character read, you get an RXRDY status signal - piece of cake! But extra hardware (a pity the 8051 can't work in sync mode).

Regards,

Richard

PS. Maybe I should tidy all this up & post it to 8052.com?

----- Original Message -----
From: David Kaleta
To: Richard W. King
Sent: Friday, August 04, 2000 1:56 AM
Subject: Re: Panasonic ZU-M2121S451 mag. card reader...


Hi Richard,

Inorder to avoid the timing nightmare there might be, I was thinking of using the 74hc590 8 bit binary counter register chip. The company I work for uses them to count rain bucket tips inorder to get the inches of rain fall. Interfaces easily to the 80c31. We could experiment with a card we choose. Make the 80c31 do a count of the data on the card. Then write that number as a "password" to have it do what we want. How does that sound?
Nuts and Volts is an electronics magazine. About $20 for a year subscription. Goto www.nutsvolts.com for more info. It has alot of good info and sources for electronic stuff.

TTYL,

Dave Kaleta"