ProSoft Technology 5201-DFNT-ASCII - Manual (Page 10)

ASCII ♦ ProLinx Standalone Functionality
Generic ASCII Serial Communication Module
Page 10 of 40 ProSoft Technology, Inc.
July 7, 2008
2.1.1 Receive Data
Data received by the receive driver is placed in the module'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.
Word Offset Description
0 Receive sequence number. This register is incremented by the Module's Receive
Driver for each new packet received.
1 Number of characters transmitted (0 to 255) from last transmit request.
2 Number of characters (0 to 256) in receive block (3 to 130).
3 to 130 Received data on port.
The first word of the data block is used to signal when new receive data is
available. Word 1 of the block contains the number of bytes in the last message
transmitted on the port. Word 2 contains the number of bytes in the received
message data area. Words 3 to 130 contain the data received. If the module 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.
2.1.2 Transmit Data
Data to transmit by the transmit driver is placed in the module's internal database
in a fixed format at the location selected by the user. The transmit driver is
disabled if the database start location is set to a value of -1. The following table
shows the structure of transmit data.
Word Offset Description
0 Transmit sequence number. This number is incremented by the user's application
for each new packet to transmit.
1 Number of characters received (0 to 256) from last receive request.
2 Inter-character delay for this message (milliseconds between characters)
3 Number of characters to transmit on Port (0 to 255)
4 to 131 Data to transmit on port
The first word of the data block is used to signal when new transmit data is
available. Word 1 of the block may optionally contain the number of characters
processed in the last receive message. Word 2 of the message is used to pace
the characters during the transmission process. This may be required when
interfacing with slow ASCII devices (that is, modems in command mode).