ib technology

4

Host Driver software

Communication with the MicroRWD module is via the TTL level RS232 interface (9600

baud, 8 bit, 1 stop bit, no parity) and uses the CTS line for hardware handshaking. The

Windows applications (supplied with the Evaluation kit) can be used to communicate with the

module or the user can write their own application on a PC or a microcontroller. The

following basic communication algorithm should be used:-

Typical host computer “pseudo” driver code

if (Green LED ON (pin 2 = 0))

// Optional check for valid tag in field

{

if (CTS = 0)

// Wait for CTS = 0 (RWD ready to receive command / data)

{

// CTS times out after 10ms so command and all parameters must be sent with no-

// gaps otherwise CTS times out and goes HIGH.

// For example, send READ PAGE 1 (0x52 0x01)

SEND_CMD( );

// Sent command + parameters to RWD

// RWD sets CTS = 1 after last parameter received. RWD module enters low-

// power state during (programmable) polling delay then sends reply.

GET_REPLY( );

// Get Acknowledge byte + data

// Response to READ command is 0xC0 (no tag) or 0xD6 + four bytes of DATA.

}

}

b0

b1

b2

b3

b4

b5

b6

b7

b8

b9

5v

0v

idle

START

8 bit data

STOP idle

1

0

TTL levels

5v

0v

5v

0v

5v

0v

RWD

BUSY

RWD

RX

RWD

TX

Ready to Receive

Ready to Receive

RWD cannot receive CMD or DATA

CMD/DATA

CMD/DATA

DATA

Repeated RWD polling cycle and serial communication BUSY protocol

Transmitted or Received data byte, 9600 baud, 8 bit, 1 stop, No parity (104uS per bit)

Polling delay (100mS to 600mS)

100mS default

Host must Transmit CMD/DATA within 10mS of BUSY going low

Busy