ib technology

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3) Host commands received and processed.

When the RWD receives commands from the host computer, the polling rate increases

to allow a quick response to the command. This means that commands such as READ

or WRITE BLOCK can be repeated quickly and the large amounts of data read from,

or written to the card as fast as possible.

The polling cycle delay in this case is effectively the minimum, so the RWD responds

to the host command immediately after the RF communication is complete.

Example a) NO card present, single CARD UID (0x55) command received.

Note: at 9600 baud serial communication rate, a single byte is received or transmitted in

approximately 1mS (104µS per bit). If no commands follow then the polling rate reverts

back to the stored parameter value as in (1).

Example b) Mifare card in field, single CARD UID (0x55) command received.

5v

0v

Polling cycle

repeats

CTS

TTL levels

7ms

Not to scale

Polling cycle period set by EEPROM

parameter (4ms to 8 seconds)

Command byte received +

6mS CTS timeout

6ms

10ms

RWD

RX

(1ms) Command byte received

5v

0v

RWD

TX

Acknowledge byte reply

(1ms)

5v

0v

Host waits for CTS falling edge then sends command byte.

RWD processes command, RF turned ON for brief period to check if card present.

RWD then replies with acknowledge byte (+ data).

1

2

3

1

2

3

5v

0v

Polling cycle

repeats

CTS

TTL levels

7ms

100ms polling delay

(card still present)

6ms

23ms

RWD

RX

(1ms) Command byte received

5v

0v

RWD

TX

Acknowledge byte + 7 byte serial number reply

5v

0v

1

2

3

Command byte received +

6mS CTS timeout

Not to scale

15ms

8ms