EM4450

EM4550

Copyright

 2003, EM Microelectronic-Marin SA

7

www.emmicroelectronic.com

Selective Read Mode

The Selective Read Mode is used to read other data than that defined between FWR and LWR. To enter Selective Read

Mode, the Transceiver has to send during LIW a Receive mode pattern (RM) to turn the EM4450/4550 in Receive Mode.

Then the Selective Read Mode Command is sent by the transceiver followed by the First and Last addresses to be read.

The FWR and LWR are then replaced by the new addresses and the chip is operating in the same way as the Standard

Read Mode. The control word is not modified by this command, and the next standard read mode operation will work with

original FWR and LWR (Selected area is read once and then the chip returns to Standard Read Mode).

To read words which are Read Protected, a Login command has to be sent by the transceiver prior to the Selective Read

command. The Login command is to be used only once for all subsequent commands requiring a password.

The Selective Read mode command is followed by a single 32-bit word containing the new first and last addresses. Bits 0

to 7 correspond to the First Word Read and bits 8 to 15 correspond to the Last Word Read. Bits 16 to 31 have to be sent

but are not used in the chip. The parities must be sent according to the word organisation as described in fig.7. Note that

bit 31 is transmitted first.

To read the device Identification or the Serial Number, the Selective Read Command allows direct access to the Laser

programmed words. These words can also be addressed in the standard read mode by selecting the addresses

accordingly.

Fig. 10

XX

XX

XX

XX

XX

XX

XX

XX

P3 XX

XX

XX

XX

XX

XX

XX

XX

P2

LW7 LW6 LW5 LW4 LW3 LW2 LW1 LW0 P1 FW7 FW6 FW5 FW4 FW3 FW2 FW1 FW0 P0 PC7 PC6 PC5 PC4 PC3 PC2 PC1 PC0 "0"

Addresses Bit Stream Format

First bit receiv ed

Fig. 11

Reset Command

The Reset Command will return from any mode to the Standard Read Mode. The next word out is the FWR.

Fig. 12

Login

The Login command is used to access protected memory areas. This command has to be used only once to perform

several password protected commands. The Power-On-Reset sequence and the Reset command will reset the password

entry, and a new Login command has to be received to perform further password protected operations.

Upon reception of a correct password, the EM4450/4550 will respond with an acknowledge pattern (ACK) and then

continue in Standard Read Mode. If the Login is correct then password protected operations are allowed. If the password is

incorrect, a NAK pattern is issued and password protected operations will not be possible (refer to Write Word for password

data structure).

Fig. 13

WORD n

LIW

RM Selective RD ADDRESSES

ACK/NAK LIW

LIW

FWR

LIW

t

pp

output

input

WORD n

LIW

RM

LOGIN

PASSWORD

ACK/NAK LIW

LIW

FWR

LIW

t

pp

output

input

WORD n

LIW

RM RESET

LIW

LIW

FWR

LIW

t

pp

output

input

t

init

ACK/NAK