ProSoft Technology PLX3 Series User Manual page 154

ASCII Protocol
User Manual
Receive Data
Data received by the receive driver is placed in the gateway's internal database
in a fixed format at the location selected by the user. The receiver driver is
disabled if the database start location is set to a value of -1. The following table
shows the structure of the received data.
Description
Word Offset
Receive sequence number. This register is incremented by the gateway's Receive
0
Driver for each new packet received.
Number of characters transmitted (0 to 255) from last transmit request
1
Number of characters (0 to 256) in receive block (9 to 136)
2
Receive State
3
-1 = Listening for data
1 = Receiving port data
Total receive character count
4
Total receive message count
5
Transmit State
6
0 = Waiting for data to send
1 = RTS on
2 = RTS timeout
3 = Sending data
4 = Waiting for RTS off
5 = RTS turned off
30 = Intercharacter delay
31 = Intercharacter delay
32 = Intercharacter delay
100 = Message delay before transmit
101 = Message delay before transmit
Total transmit character count
7
Configuration error word
8
Received data on port
9 to 136
An incremented received sequence number in Word 0 signals that new data is
available in Words 1, 2, and 9 through 136. (Words 3 through 8 are updated
continuously by the gateway, whether or not the port is receiving messages.)
If the gateway is configured to swap the data bytes received, the receive driver
will swap the bytes in each word received before placing the data into the data
block. Because the data received may contain an odd number of bytes, the
length of the message received will be incremented by 1 when an odd number of
bytes are received and the swap option is utilized. This is to avoid losing the last
byte of data in the message.
Page 154 of 218
PLX3x Series
Ethernet and Serial Gateways
ProSoft Technology, Inc.
May 26, 2016