PCF7936AS datasheet(14/32 Pages) PHILIPS

14 / 32 page

NXP Semiconductors

Product Specification

Security Transponder (HITAG2)

PCF7936AS

2010 May 04

CONFIDENTIAL

7.3.1

Command Description

The general form of a control sequence consists of the

command sequence send to the transponder and an

Equalizer pattern (EQ) and Response received from the

transponder. The general control sequence timing is shown

in Figure 8.

When switching from SEND to RECEIVE and vice versa,

the basestation and control software have to consider the

indicated delays (tWAIT,Tr and tWAIT,Bs), during which the

basestation must not transmit any data or commands.

Depending on the command, the Command Sequence

consists of a minimum of 5 bit respectively 10 bit. For data

integrity reasons memory read and write commands have

to be transmitted in normal coding and in inverted coding

before being accepted by the device, which yields a

minimum Command Sequence of 10 bit.

The Equalizer, EQ, consist of a 5 bit pattern (all ones) for

basestation

settling

and

software

synchronization

purposes. The device response consists of a command

acknowledgment and/or the requested data.

Some operations require additional parameter to be send to

and/or to be received from the device, e.g. WRITE_PAGE

or START_AUTH.

For proper operation, command execution by the device

must not be suspended for more than the specified Idle

time (tIDLE), see Figure 9. Otherwise the device may stop

command decoding, disabling any communication with the

device. In this case, a LF Field Power-On Reset has to be

applied, in order to reset and initialize the circuitry, see

section 7.7. Consequently, the device resumes WAIT state.

As indicated, the Idle time is specified as the time interval

between the last bit received from the transponder and the

last

bit

the

Command

Sequence

send

the

transponder.

Some

commands

allow

repeating

the

command

several

times

for

data

integrity

reasons,

however, in any case the limitations imposed by the Idle

time have to be considered.

The Idle time applies also for the very first command send

to the device after a device LF Field Power-On Reset

condition, see also section 7.7.

SEND to

Transponder

RECEIVED from

Transponder

Command Sequence

Response

Parameter

tWAIT,Tr

Parameter

tWAIT,Tr

tWAIT,Bs

Figure 8. General control sequence timing

tIDLE

SEND to

Transponder

RECEIVED from

Transponder

Response / Parameter

tWAIT,Tr

Command Sequence

Figure 9. Command Idle Time

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