R
EM4150
EM4350
Write Password
When a Write Password command is received, the chip next expects information on the actual valid password. The chip
sends back an ACK pattern if the password is correct. Then the chip expects the new password consisting of 32 bits +
parity bit to be stored in the EEPROM. The chip will respond with an ACK pattern for a correct reception of data upon
reception of the new password, and then will send another acknowledge pattern (ACK) to announce that the data is stored
in the EEPROM.
The Read after Write function has no effect on this command. If the password is wrong or the
transmission is faulty, the chip will : send a NAK pattern; return to the Standard Read Mode; and, the password will remain
the same. (Refer to Write Word for password data structure).
tpp
twa
twee
OUTPUT
INPUT
ACK
LIW
LIW
FWR
LIW
ACK
ACK
WORD n
LIW
RM WRITE PW
ACTUAL PW
RM
NEW PW
TRANSCEIVER RF FIELD "ON"
Fig. 15
Write Word
The Write mode allows modification of the EEPROM contents word by word. To modify address 1 (Protection word) and
address 2 (Control word), it is mandatory to first send a Login command in order to Log in (like in a computer). The new
written values will take effect only after performing a Reset command. It is strongly recommended to check the result of
modifying the contents of these addresses effecting the function of the chip. Address 0 (Password) cannot be modified with
this command but can be changed with the Write Password command.
Addresses 3 to 31 are programmable according to the defined protections. If the Password Check bit is off (bit 16 of control
word) and the word is not write inhibited, the selected word can be freely modified without password. If the Password Check
bit is on and the word is not write inhibited, the selected word can be modified with a previous Login. In any case, if the
word is write inhibited, the protection word has to be changed before programming can occur.
Write to Address
Check Password bit
Write Inhibit
Write Operation
(16 bit / Control word)
(Protection word)
0
X
X
X
OFF
ON
X
X
OFF
ON
OFF
OFF
ON
Only with Write Password command
Login always required
Write configuration LOCKED
Freely programmable
Login required
Change protection word first
1 – 2
1 – 2
3 – 31
3 – 31
3 – 31
Address
0
0
A5 A4 A3 A2 A1 A0
Note :
Padd
A5 in write mode always "0"
(addresses Laser ROM)
First bit received
Data
D31 D30 D29 D28 D27 D26 D25 D24 P3 D23 D22 D21 D20 D19 D18 D17 D16 P2 D15 D14
D13 D12 .......................... D02 D01 D00 P0 PC7 PC6 PC5 PC4 PC3 PC2 PC1 PC0 "0"
Fig. 16
The Write Word command is followed by the address and data. The address consists of a 9 bit block containing 8 data bits
and 1 even parity bit. Only 6 bits from the data section are used for the word addressing, and the first three bits sent must
be "0". The data consists of 4 times 9 bit blocks, each block consisting of 8 data bits and 1 associated even parity bit and
one additional block consisting of 8 column parity bits and "0" as stop bit (Refer to fig. 7)
7
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