Rockwell Automation 1771-SPI,D17716.5.122 SPI PROTOCOL INTERFACE - Manual (Page 16)

Important Information That You Need
to Set Up the SPI Network
Chapter 2
2-2
Important: When using any of these devices with a custom configuration
(as described in this manual) rather than a standard configuration
(described in the SPI Protocol Interface Manual), you use the above ID
codes, but you must set the Configuration Select (CS) bit (bit 14 in MCC
word 5, 7, 9, etc) when you enter the device polling list in the MCC.
(We describe the MCC and other data files in chapter 3.)
Address Code to Identify the Device on the SPI Network
The SPI module uses the address code that you set on the device, in
combination with the SPI-assigned device ID code, to locate the device on
the SPI network. This lets the SPI module differentiate between two or
more devices having the same device ID. However, we recommend that
your program be structured to communicate with no more than one device
of a given type at a time. The use of two or more devices of the same type
may require special considerations described elsewhere in this manual.
The address code is an 8-bit code with a decimal range of 32-255.
How to Set the Address Code in the Device
Most devices will typically use jumpers or a switch assembly to set the
address code. More complex devices such as a multi-zone temperature
controller may use a keypad to set the device address and zone addresses.
You must get this information from the manufacturer if not included in the
user manual that accompanied the device.
Communication Rate
Typical communication rates vary from 1200 to 19200 baud. You select a
communication rate that suits all devices on your SPI network. The device
with the lowest maximum rate establishes the upper limit for the network.
The device manufacturer must tell you the range of selectable rates, and
how to select a given rate.