Edwards Signaling 5530M-485 - Manual (Page 6)

P/N 3100345 ISSUE 2 PAGE 6
Note: In the event that a bad checksum is calculated, by the receiving unit, it will reply with a <NAK>
character instead. The <NAK> character has a value of 15 hexadecimal.
<ETX> The <ETX> character has a value of 3 hexadecimal and is required at the end of
every message (1 byte)
<CHKSUM> Receiving unit calculates two-byte checksum and returns ASCII value. Refer to
Section 4.0 for Block checksum calculation and verification.
Example 1: <STX>014300A<ETX>00
Unit 01 is being polled and programmed to Zone A
Unit Response: <STX>0143DA<ACK><ETX>56
The unit returned a <STATUS> ‘D’ for its current diagnostic state and an <ACK>
character because both message and checksum are valid. The unit is not actively
playing Tone/Message. The calculated two-byte message checksum was ‘56’.
Example2: <STX>014300A<ETX>00
Unit 01 is being polled and programmed to Zone A. Unit 01 is currently playing a
Tone/Message.
Unit Response: <STX>0143BA<ACK><ETX>54
The unit returned a <STATUS> ‘B’ for its current diagnostic state and an <ACK>
character. The unit is actively playing a Tone/Message at the time this command
was received. The calculated two-byte message checksum was ‘54’.
3.4 TIME SEQUENCE, TIME REMAINING COMMAND - 44
Send Format:
<STX><UA>44 00 <ZONE> <ETX> <CHKSUM>
<UA> Unit address characters (2 bytes). See Section 2.0, Messaging Format
<44> Two byte ASCII Command denoting a Time Sequence (2 bytes).
<00> Two byte ASCII ‘00’ used as protocol padding (two byes)
<ZONE> Programmable unit Zone issued by the master or controlling computer
Range ASCII A-D (1 byte).
<ETX> The <ETX> character has a value of 3 hexadecimal and is required at the end of
every message (1 byte)
<CHKSUM> Optional two byte Message Block checksum (2 bytes). Refer to Section 4.0 for
Block checksum calculation and verification. If checksum is not desired, must pad
these two bytes with two ASCII zeros 00.
Unit Response: <STX><UA> 44 <TIME LEFT><ACK><ETX> <CHKSUM>
<UA> Unit address characters (2 bytes). See Section 2.0, Messaging Format
<44> Two byte ASCII Command 43 echoed back from the receiving unit (2 bytes).
<TIME LEFT> Represents seconds left, in hexadecimal format, until the unit stops playing active
Tone/Message. Range 00-63 hex (2 bytes). The unit’s internal counter returns the
time remaining in seconds represented by a two byte hexadecimal value in the
above data field.
Note: For non-timed events, the unit returns two ASCII zeros ‘00’.
<ACK> Unit received a complete message and checksum characters are valid.
Note: In the event that a bad checksum is calculated, by the receiving unit, it will
reply with a <NAK> character instead. The <NAK> character has a value of 15
hexadecimal.
<ETX> The <ETX> character has a value of 3 hexadecimal and is required at the end of
every message (1 byte)
<CHKSUM> Receiving unit calculates two-byte checksum and returns ASCII value. Refer to
Section 4.0 for Block checksum calculation and verification.
Example 1: Prior to issuing Command 44, the master issues a 99 second timed sequence event
for Tone/Message 03 to play on unit address 1F.