SPI Protocol
The Society of the Plastics Industry (SPI) communication protocol specifies a connection
management Protocol, a packetized communication format, and communication error
mechanisms passing commands and data between a host computer and a slave. A host
computer initiates all communications. The protocol used corresponds to the 3.01 version of
the SPI communication protocol specification dated October 1990. The data is transmitted
via
a multi-drop EIA485 (half-duplex) hookup. The controller will support a number of
commands
that will allow the host computer to retrieve status and assign setpoints. The commands
correspond to a mold temperature controller device.
Commands Descriptions
(20H) Echo poll-Controller integrity command. Return the 4 bytes of ASCII assigned
by the Echo Select command in an open format.
(21H) Echo Select -Controller integrity command. Supplies 4 bytes of ASCII in an open
format that is to be returned when an Echo Poll command is received.
(22H) Version poll-Returns a version number (MBB =0101) as 4 bytes of ASCII in an
open format where: AA = SPI assigned version level, BB = Vendor assigned
version level
(30H) Setpoint poll - Returns the current process setpoint value in numeric format.
(31H) Setpoint select -Assigns a value to the process setpoint in numeric format.
(32H) Alarm, high temperature deviation poll -Return the high temperature deviation
setpoint value in numeric format. This value when added to the process setpoint
gives the temperature at which a high alarm will occur.
(33H) Alarm, high temperature deviation select -Assigns a value to the high
temperature deviation setpoint in numeric format.
(34H) Alarm, low temperature deviation poll -Returns the low temperature deviation
setpoint value in numeric format. This value when subtracted from the process
setpoint gives the temperature at which a low alarm will occur.
(40H) Status process poll -Returns the status of the process as 16 flag bits in open
format. The following bits are supported. The rest are set to 0.
Bit 0 - Processing
Bit 1 -Alarm, System
Bit 2 -Alarm, Process
Bit 3 -Alarm, Machine
Bit 4 -Alarm, High Temperature
Bit 5 -Alarm, Low Temperature
Bit 7 -Alarm, Low Pressure
Bit 9- Alarm, Low Flow
(42H) Status, machine 1 poll - Returns the status of the machine as 16 flag bits in open
format. The following bits are supported. The rest are set to 0.
Bit 0 - Processing
Bit 1 -Alarm, System
Bit 2 -Alarm, Process
Bit 3 -Alarm, Machine
Bit 4 -Alarm, High Temperature
