ib technology

4

Command Protocol

The following commands are supported. The corresponding acknowledge code should

be read back by the host and decoded to confirm that the command was received and

actioned correctly. The serial bit protocol is 9600 baud, 8 bits, 1 stop, no parity (lsb

transmitted first).

The status flags returned in the Acknowledge byte are as follows:

b7 b6 b5 b4 b3 b2 b1 b0

1

1

1

1

1 1 1 1

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EEPROM error (Internal EEPROM write error)

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| Tag OK (Tag identity code matched to list and Password exchange successful)

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| Rx OK (Tag communications and acknowledgement OK)

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RS232 error (Host serial communications error)

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RELAY Enabled flag

HTRC (or Antenna fault) error flag

Note that bits 6 and 7 are fixed 1’s so that an acknowledge code of D6 (Hex) would

generally indicate no errors with a matched (or authorised) HT2 Tag present.

Note also that only the relevant flags are set after each command as indicated in the

following specification.

Write Tag

Command to write 4 bytes of data to HT2 32 bit page. If the write was unsuccessful

(invalid tag or out of field) then Status flags in acknowledge byte indicate error.

B7

B0

Command:

0 1 0 1 0 1 1 1

(ASCII “W”, 0x57)

Argument1:

x x x x x N N N

(N = HT2 page address 0-7)

Argument2:

D D D D D D D D

(D = msb data to write to HT2)

Argument3:

D D D D D D D D

Argument4:

D D D D D D D D

Argument5:

D D D D D D D D

(D = lsb data to write to HT2)

Acknowledge:

1 1 F F F F F X

(F = Status flags)

Note that PASSWORD exchange occurs for WRITE command.

If no tag present then acknowledge / status byte reply is 0xC0

If tag present but RWD PASSWORD check fails then acknowledge byte reply is 0xC0.

If tag present but TAG PASSWORD check fails then acknowledge byte reply is 0xC4.

If tag present and both PASSWORDS match then acknowledge reply is 0xD6.