Dear Santosh

Thanks for the feedback. I thinking I am exactly doing this but still have a problem


We are interfacing SLE4428 card to AT89C52 where the pins of SLE4428 are connected to controller in following way.

RST : P2.7
CLK : P2.6
IO : P2.5
Internal Signal : P2.4

We are able to read the card written using reader/PC software. We are however unable to write any data to the card.
Note that we are using the Siemens documentation ( Datasheet 04.94 ).

STEPS FOR PSC VERIFICATION :

A) we write the Error Counter:

1- send 4fH ; op code for write the error counter (corresponding to S0S1S2S3S4S5A8A9)
2- send 0fdh ; for add error counter (corresponding to A7-A0)
3- send 0feh ; counter value (corresponding to D7-D0)
*********************************
then
we clear clock and set the i/o line (by writing IO = 1)
Then we send 102 clock
where i/o line goes to 0 indicating end of write operation.
**********************************

B) PSC Verification Procedure:

i. send first psc byte:

1-send byte ;b3H code for PSC vrify (corresponding to S0S1S2S3S4S5A8A9)
2-send byte ;0feH addr of PSC byte1(corresponding to A7-A0)
3-send byte ;a7H psc code (corresponding to D7-D0)
wait for i/o goes to high

ii. send second psc byte

1-send byte ;b3H code for PSC vrify (corresponding to S0S1S2S3S4S5A8A9)
2-send byte ;0ffH addr of PSC byte1(corresponding to A7-A0)
3-send byte ;a7H psc code (corresponding to D7-D0)

wait for i/o goes to high

********************************

After sending 2 PSC bytes :

. We give Delay of 4 Microsec
. Make CLK =1 for 10 Microsec
. Make CLK =0 for 10 Microsec
// by now io should go LOW indicating end of verification
. Make CLK =1 for 10 Microsec
. Make CLK =0 for
io goes low indicating end of verification.

Now at this stage if verification is correct then we should be able to
erase the Error Counter but we are not able to do it using Procedure A)

Also if verification is correct we should be able to write at any address
using one of the following procedures given in datasheet for writing
without protect bit.

1. WriteOnly
2. EraseOnly
3. EraseAndSubsequentWrite
But we are failing to do this also.

I feel that in the datasheet the confirmation for Correct PSC verification is not given.

My doubts are :

1.Initially the Error Counter was FF and with your procedure of entry code it became FE but
now we cannot make it FF with the same procedure.
2.How to make IO high after sending the 3 bytes of Command when RST is still high.Because
making IO = 1 requires RST changing from 0 to 1.