PCF7936AS datasheet(19/32 Pages) PHILIPS

19 / 32 page

NXP Semiconductors

Product Specification

Security Transponder (HITAG2)

PCF7936AS

2010 May 04

CONFIDENTIAL

WRITE_PAGE

The command WRITE_PAGE writes the data supplied with

this command into the designated page. The page

designated for writing is specified by the command bits pg2

to pg0. For data integrity reasons the 5 bit command and

its complement have to be send, before the device will

accept it, see Figure 15. If accepted, the command

Response

consist

the

command

itself,

and

the

corresponding complement.

The 10 bit command sequence may be repeated several

times, if desired, to increase the data integrity level. In the

case that one of the 5 bit commands and its complement

do not match, an error condition occurs that causes the

device to terminate the command, to initialize the device

and to enter the WAIT state. No command Response will

be send by the device in this case nor does the designated

page being overwritten.

After termination of tPROG the device checks, if the

EEPROM write operation completed successfully, if not, an

error condition occurs that causes the device to enter the

WAIT state.

the

case

the

write

operation

did

not

complete

successfully, the designated EEPROM page may hold an

undefined content or may suffer from a weak programming.

In order to unambiguously verify, whether programming of

the designated page completed properly, the basestation

has to identify, if the device still resides in AUTHORIZED

state or entered WAIT state. Thus, a READ_PAGE or

READ_PAGE_INV

command

should

issued

subsequently and monitored, if this command executes

properly.

If the device still resides in AUTHORIZED state, command

execution would complete successfully and after verifying

the data that has been read, proper operation of the

corresponding WRITE_PAGE command can be assumed.

Subsequent commands may be issued after termination of

the final tWAIT,Bs.

Any attempt to write a page that is protected against

overwriting will be detected and cause an error condition,

upon which the device terminates the command during

tWAIT,Tr and enters the WAIT state. No Response will be

send in this case.

If the device is configured for Password mode (ENC = 0)

the command sequence is transmitted in plain, while in

Cipher mode (ENC = 1) the whole command sequence is

transmitted ciphered.

SEND to

Transponder

RECEIVED from

Transponder

1 1 1 1 1

tWAIT,Tr

tWAIT,Bs

1 0, pg2, pg1, pg0

CM[4:0]

bit 31 ..............bit 0

tWAIT,Bs

tPROG

1 0, pg2, pg1, pg0

CM[4:0]

WRITE_PAGE

0 1, pg2, pg1, pg0

CM[4:0]

0 1, pg2, pg1, pg0

CM[4:0]

tIDLE

Data

SEND to

Transponder

RECEIVED from

Transponder

Figure 15. WRITE_PAGE timing

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