SLE4428 Datasheet, PDF (7/17 Pages) Siemens Semiconductor Group – ICs for Chip Cards

SLE 4418
SLE 4428
1 Functional Description
1.1 SLE 4418
The chip contains an EEPROM organized 1024 x 8 bit offering the possibility of programmable write
protection for each byte. Reading of the whole memory is always possible. The memory can be
written and erased byte by byte. Input data and the contents of the adressed byte are compared so
that only bits are written which were not written before. Erasing is only possible byte-wise, even if
only one bit is to be erased, but bits may be written individually. Each byte can be write/erase-
protected individually by setting a protect bit (EEPROM → ROM). The protect bit is only one time
programmable and cannot be erased.
1.2 SLE 4428
Additionally to the above functions this version has a PSC verification logic. All the memory, except
for the PSC, can always be read. The memory can be written or erased only after PSC verification.
The error counter can always be written. After eight successive incorrect entries the error counter
will block any subsequent attempt at PSC verification and hence any possibility to write and erase.
2 Reset and Answer-to-Reset
2.1 Reset
When the operating voltage is applied, the chip goes into the power-on reset (POR) state. POR is
terminated by reset. Reset is started by RST changing from “0” to “1” and finished by CLK going
from “0” to “1”. This reset operation aborts any currently active command. After POR a read
operation must be performed before any change of data is possible.
2.2 Answer to Reset (ISO 7816)
Answer to reset sets the address counter to “0” and the first data bit appears on the output. The
contents of the following addresses can be read out with the following clock pulses. Answer to reset
is executed by the following steps (Fig. 2) :
– RST goes from “0” to “1”,
– clock pulse is applied,
– RST changes back from “1” to “0”.
3 Commands
The state of RST defines the data direction on I/O.
RST
1
0
I/O
Command entry
Data output
Semiconductor Group
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