14
Table 12 - SPI Parameters
Command
Poll
Select
Description
Echo
20 20
20 21
This is the controller integrity command used to accept and retain data and provide it
in response to a poll inquiry. This is an open 4 byte ASCII format with ASCII units.
Version
20 22
This is the controller version command used to provide a version number following
format: AABB, where AA = SPI assigned version level, BB = vendor assigned version
level. This is in an open 4-byte ASCII format with ASCII units.
Setpoint Process
Temperature
20 30
20 31
This is the temperature target for the supply coolant leaving the chiller. This is a
numeric format in °F.
Alarm, High Temperature
Deviation
20 32
20 33
This is the value, in conjunction with the process setpoint that determines the high
alarm temperature. This value must always be positive. This is a numeric format in °F.
Alarm, Low Temperature
Deviation
20 34
20 35
This is the value, in conjunction with the process setpoint that determines the low
alarm temperature. This value must always be positive. This is a numeric format in °F.
Status, Process
20 40
This is the process status in a 16 bit format as follows:
0 = Controlling
1 = An alarm is present
2 = An alarm affecting the process has occurred (high or low temperature deviation)
3 = An alarm affecting the machine has occurred (probe fault or pump fault)
4 = The controller has exceeded its over setpoint deviation
5 = The controller has exceeded its below setpoint deviation
Status, Machine 1
20 42
This is the machine status in a 16 bit format as follows:
0 = Controlling
1 = An alarm is present
2 = An alarm affecting the process has occurred (high or low temperature deviation)
3 = An alarm affecting the machine operation has occurred (probe fault or pump fault)
4 = The controller has exceeded its over setpoint deviation
5 = The controller has exceeded its below setpoint deviation
Status, Machine 2
20 44
This is the machine status in a 16 bit format as follows:
0 = Controlling
1 = An alarm is present
2 = An alarm affecting the process has occurred (high or low temperature deviation)
3 = A sensor error has been detected
4 = An alarm affecting the machine operation has occurred
Mode, Machine
20 48
20 40
This is the machine mode in two 8-bit bytes.
When polling 20 48 bit 0 indicated the machine is off
20 40 bit 0 commands the unit to be turned on or off (on when high or off when low)
20 40 bit 1 is used to recognized the alarm condition
Temperature, To Process
(Supply)
20 70
This returns the process supply temperature.
This is a numeric format in °F.
Temperature, To Process
(Return)
20 72
This returns the process return temperature.
This is a numeric format in °F.
