SLE4442 Siemens, SLE4442 Datasheet - Page 23

• Manufacturer Part Number: SLE4442
• Description: (SLE4432 / SLE4442) 256 Byte EEPROM
• Manufacturer: Siemens

2.4
The SLE 4442 requires a correct verification of the Programmable Security Code PSC stored in the
Security Memory for altering data if desired.
The following procedure has to be carried out exactly as described. Any variation leads to a failure,
so that a write/erase access will not be achieved. As long as the procedure has not been
successfully concluded the error counter bits can only be changed from “1” to “0” but not erased.
At first an error counter bit has to be written to “0” by an UPDATE command (see figure 11) followed
by three COMPARE VERIFICATION DATA commands beginning with byte 1 of the reference data.
A successful conclusion of the whole procedure can be recognized by being able to erase the error
counter which is not automatically erased. Now write/erase access to all memory areas is possible
as long as the operating voltage is applied. In case of error the whole procedure can be repeated as
long as erased counter bits are available. Having been enabled, the reference data are allowed to
be altered like any other information in the EEPROM.
The following table gives an overview of the necessary commands for the PSC verification. The
sequence of the shaded commands is mandatory.
Command
Read security Memory
Update Security Memory
Compare Verification Data
Compare Verification Data
Compare Verification Data
Update Security Memory
Read Security Memory
As shipped, the PSC is programmed with a code according to individual agreement with the
customer. Thus, knowledge of this code is indispensable to alter data.
Semiconductor Group
PSC Verification (SLE 4442 only)
31
Control
B7…B0
31
39
33
33
33
39
H
H
H
H
H
H
H
Address
A7…A0
No effect
00
01
02
03
00
No effect
H
H
H
H
H
21
Data
D7…D0
No effect
Input data
Input data
Input data
Input data
FF
No effect
H
Remark
Check Error Counter
Write free bit in Error
Counter input data:
0000 0ddd binary
Reference Data Byte 1
Reference Data Byte 2
Reference Data Byte 3
Erase Error Counter
Check Error Counter
SLE 4432
SLE 4442