Rockwell Automation 1771-SPI,D17716.5.122 SPI PROTOCOL INTERFACE - Manual (Page 13)

Overview of an SPI Communication Network
Chapter 1
1-7
The SPI specification and previous revisions of the SPI module user
manual use terms that may be unfamiliar to you. We attempt to translate
SPI terms to ones more commonly used on the shop floor so you can more
easily understand concepts of SPI module operation.
SPI Terminology
SPI Term How it works or what it means ShopĆfloor Term
ASCII Polls ASCII strings such as SPI Revision returned by BTR ASCII status word (32Ćbit word or 2 PLC words)
ASCII Selects ASCII strings that you send to the SPI module ASCII string (32Ćbit word or 2 PLCĆ5 words)
Bit Polls bitĆlevel status words returned by BTR bitĆstatus words (16Ćbit words)
Bit Selects bitĆlevel command words that you send to the SPI module bitĆcommand words (16Ćbit words)
Device ID SPIĆspecified code for an SPIĆspecified device 8Ćbit code such as 00100010 (22) for a dryer
Device Type SPIĆspecified device mold temperature controller, dryer, hot runner, etc.
Numeric Polls process actuals such as pressure or flow returned by BTR numeric status words (32Ćbit word or 2 PLCĆ5 words)
Numeric Selects setpoints or alarm limits that you send to the SPI module numeric setpoints (32Ćbit word or 2 PLCĆ5 words)
Polls (noun) status returned to the processor by BTR Numeric status, or words containing status bits
Selects (noun) commands transferred to the SPI module by BTW setpoints, or words containing control bits
Station Address address that you select for a device on the SPI network device address
Version latest update revision level
Zone applies to temperatureĆcontrol devices such as hot runner:
independently controlled area, slave to master controller
such as the barrel, nozzle, or runner, on a molding machine
zone or temperature zone
Zone Addresses slave addresses for a single temperature control device zone address
Other Important Terms
Term Definition
Command bitĆlevel such as to turn ON a device, or wordĆlevel such as a setpoint or alarm
Decimal Data the PLCĆ5's baseĆ10 (integer) numbering system with a range of -32,768 to +32,767,
stored in N files as 2'sĆcomplement binary in 16Ćbit words
Polling Sequence or
Automatic Polling
The manner in which the SPI module pulls status from each device on the SPI link, formats it,
and sends it to the PLC processor by BTR. The SPI module services the devices (completes
one before going to the next) in the order that you listed them in the MCC polling sequence.
Status bitĆlevel such as the ON/OFF status of a device, or wordĆlevel such as a process temperature
Definition of Terms