Download Modicon XMIT Function Block User Guide

Source and Destination Data Areas for Function Codes (20, 21)
Function Code
Master PLC Data Area
Slave PLC Data Area
20 (Read general reference 6x)
4x (destination)
6x (source)
21 (Write general reference 6x)
4x (source)
6x (destination)
When you want to send 20 Modbus messages out of the PLC, you must
program 20 Modbus definition tables and then through ladder logic
increment the pointer to each definition table after each successful
operation of XMIT, or you may program 20 separate XMIT blocks and
then activate them one at a time through ladder logic.
2.2.11
Message Length (4x + 10)
You enter the length of the current message. When XMIT is sending
Modbus messages for function codes 01, 02, 03, 04, 05, 06, 08, 15 and 16,
the length of the message is automatically set to five. When XMIT is
receving Terminated ASCII input the length of the message must be set
to five or an error results. When XMIT is sending Modbus messages for
function codes twenty and twenty- -one, the length of the message is
automatically set to six. When XMIT is sending ASCII messages, the
length may be 1 ... 1024 ASCII characters per message.
2.2.12
Response Time--Out (mS) (4x + 11)
You enter the time value in milliseconds (mS) to determine how long
XMIT waits for a valid response message from a slave device (PLC,
modem, etc.). In addition, the time applies to ASCII transmissions and
flow control operations. When the response message is not completely
formed within this specified time, XMIT issues a fault. The valid range
is 0 ... 65535 mS. The timeout is initiated after the last character in the
message is sent.
2.2.13
Retry Limit (4x + 12)
You enter the quantity of retries to determine how many times XMIT
sends a message to get a valid response from a slave device (PLC,
modem, etc.). When the response message is not completely formed
within this specified time, XMIT issues a fault and a fault code. The
valid range is 0 ... 65535 # of retries. This field is used in conjunction
with response time- -out (4x + 11).
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XMIT Communication Block
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