Section 6
CONTROLLER COMMUNICATION
PROTOCOL
27
6.5 MESSAGE FORMAT
Messages are RS-485 half-duplex, 9600 baud, 8 bit, 1 stop bit, no parity. Control
characters are used to frame a message. These characters mark the start of the
message and the end of the message.
All messages have the following format:
STX - Start of text. Signifies the start of a message. (0x02)
## - Two character com number
m - one character message type
d - data, one to several characters long. Multiple items are separated by commas.
xx - two character checksum, based on all characters after STX
CR - Carriage Return. CR-LF signifies end of a message. (0x13)
LF - Line Feed. CR-LF signifies end of a message. (0x10)
In the examples presented in the following section, STX, CR, and LF are not shown.
6.6 MESSAGE TYPES
Messages follow the forms listed in Table 6.2 below. Details of the data types within the
messages are listed in Section 6.7, Data Types. “N” & “M” messages are broadcast by
controllers in a sequenced system.
Remaining exchanges may be initiated by a monitor or master on non-sequenced
systems, or during the time immediately following a monitor enable in a sequenced
system.
Table 6.2 Controller Message Types
MESSAGE TYPE FORMAT EXAMPLE
N – Net status broadcast ##N19,2,23,17,18xx 01N0,115,2000,M,C88
COMMENT:
Controller’s broadcast status in stand-alone sequencing.
Data fields are:
19- Capacity in cfm
2- P2 pressure in psig
23- Sequence time in hours
17- Run Status (See DATA TYPES)
18- Mode (See DATA TYPES)
M – Monitor Enable
broadcast
##Mxx 01M52
COMMENT:
Controller’s monitor enable in stand-alone sequencing.
Time follows for queries by a monitor.
I – Information Request ##Ixx 01I56
COMMENT:
Monitor’s request for controller information. The controller
responds with i message type.
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