DPMS XPQ, Руководство пользователя

Страница: 93 / 134

91
POWER INSTRUMENTS
Framing
Address Function Data Check
8-Bits 8-Bits N×8-Bits 16-Bits
Table5.1 Data Frame Format
Address Field
The address field of a message frame contains eight bits. Valid slave
device addresses are 0~247 decimal. A master addresses a slave by placing
the slave address in the address field of the message. When the slave sends
its response, it places its own address in this address field of the response to let
the master know which slave is responding.
Function Field
The function code field of a message frame contains eight bits. Valid codes
are 1~255 decimal. When a message is sent from a master to a slave device
the function code field tells the slave what kind of action to perform.
Code Meaning Action
01 Read Relay Output Status Obtain current status of Relay Output
02 Read Digital Input(DI) Status Obtain current status of Digital Input
03 Read Data Obtain current binary value in one or more registers
05 Control Relay Output Force Relay to a state of on or off
16 Press Multiple-Register Place specific binary values into a series
of consecutive Multiple-Registers
Table5.2 Function Code
Data Field
The data field is constructed using sets of two hexadecimal digits, from
00 to FF hexadecimal. The data field of messages sent from a master to slave
devices contains additional information which the slave must use to take the
action defined by the function code. This can include items like discrete and