Dev_Tasks	
The application program running in the PLC CPU controls the timing and content of each query by sending a COMMREQ message. The COMMREQ must be addressed to the CPU serial port that is connected to the Modbus RTU serial network. COMMREQ data specifies the content of the query. When the query/response transaction completes, a COMMREQ status value indicates the success or failure of the transaction.
Reference: Modbus RTU Master Communications GFK-2220A.
#END#

CR_Task
TASK input at Commreq function block
#END#

Wait_Flag	
This flag determines whether PLC will wait until the device serial ports receive the intended data before continuing. The request can either send a message and wait for a reply, or send a message and continue without waiting for a reply. If the Command Block specifies that the program will not wait for a reply, the Command Block contents are sent to the device and ladder program execution resumes immediately. This is referred to as NOWAIT mode. If the Command Block specifies that the program will wait for a reply, the Command Block contents are sent to the targeted device and the CPU waits for a reply for a maximum length of time specified in the Command Block. If the device does not respond in that time, ladder program execution resumes. This is referred to as WAIT mode.
#END#

Idle_Tmout	
The idle timeout value is the maximum time the PLC waits for the device to acknowledge receipt of the request. For NOWAIT, this value is not used. (Any timeout value is ignored; it can be zero.) If WAIT is selected, this word specifies the idle timeout period, in 100-microsecond increments.
#END# 

Max_Comm_Tm	
This word contains the maximum amount of time the program should hold the window open when the device is busy. For NOWAIT, this value is not used. (Any timeout value is ignored; it can be zero.) If WAIT is selected, this word specifies the maximum time in 100 microsecond increments.
#END#

Initialize RTU Slave Port
Initialize RTU Slave Port is a Local command. The standard Serial Port Setup COMMREQ may be used to configure the port for Modbus RTU slave operation using configuration values specified in the data block. It may also be used to modify configuration values during Modbus RTU slave operation. Note that the usage of words 19 and 20 is different from Modbus RTU Slave. When the CPU hardware configuration assigns a different protocol to the target port and this COMMREQ is used to start Modbus RTU slave, the application must not issue additional Modbus RTU slave COMMREQs until this one completes successfully. The application must monitor the value in the COMMREQ status location do determine successful completion. When this COMMREQ is used to re-initialize Modbus RTU slave during operation, the Diagnostic Status Words are cleared.
#END#

Protocol
Protocol-Modbus RTU; Constant = 3
#END#

Data_Rate
Data Rate: The highest valid rate depends on the specific Modbus RTU slave device. For example, 19,200 bits/second (bps) is the highest data rate supported Modbus RTU Master and Slave on IC693CPU363, IC200CPU001 and IC200CPU002. IC200CPU005 and IC200CPUE05 currently support 57,600 bps.
#END#

Parity
Parity: Note that when parity = ODD or EVEN, the character length used by Modbus RTU Master is 11 bits: one start bit, 8 data bits, one parity bit and one stop bit. There is no parity bit when parity = NONE, and the character length is 10 bits. The Modbus RTU standard recommends 11 bits in all cases.
#END#

Flow_Control
Flow Control: 2 = SOFTWARE is invalid; a Parameter Error (020Ch) is returned to the status location specified in the Initialize Port COMMREQ.
When 0 = HARDWARE is specified, the port asserts RTS and waits for CTS to become active before transmitting. If CTS does not become active within 2 seconds, a time-out error code is returned to the status location specified in the Send RTU Query COMMREQ. If CTS becomes active and then is de-asserted while the port is transmitting, up to 5 milliseconds may elapse before transmission stops. The maximum number of characters transmitted after CTS is de-asserted is proportional to the data rate. These values are in addition to the character that is being transmitted at the time CTS is de-asserted. Data Rate Max. Characters after CTS is De-asserted.
*****************************************************************************************************************************************************************************************************
Data Rate 	Max. Characters after CTS is De-asserted	Data Rate 	Max. Characters after CTS is De-asserted	
*****************************************************************************************************************************************************************************************************
1200			1				19200			10
2400			2				38400			20
4800			3				57600			29
9600			5				115200			58
#END#

Turn_Delay
SNP Turnaround Delay: This value is ignored. However, the specified value must be valid (0 - 255).
#END#

TmOut
Response message time-out-the specified value must be greater than the sum of the longest receive-to-transmit delay for all slaves plus the longest response message transmission time at the current data rate. LONG = 8 Seconds; MEDIUM = 2 Seconds; STANDARD = 500 Milliseconds; SHORT  =200 Milliseconds.
When a Send RTU Query COMMREQ specifies a broadcast query, COMMREQ_OK is returned to the COMMREQ status location when this time-out expires. When a Send RTU Query COMMREQ specifies a non-broadcast query, a RESPONSE_TIMEOUT error code is returned to the COMMREQ status location when this time-out expires before a complete response is received. Modbus RTU requires a time-out in all cases. The STANDARD timeout (500 milliseconds) is recommended by the Modbus RTU standard. The time-out begins after the port has transmitted the last character of the query and stops when the character-gap time-out (Word 19) expires after the last response character is received. If the response time-out expires before the end of the character-gap time-out, the port is checked for a response message. If one is detected (for example, because the response time-out expired after the response was received but before the character-gap time-out expired), the response is processed normally after the gap timeout expires. If no valid response is detected, a time-out error code is returned to the COMMREQ status location.
#END#

Interface
Port Interface - Port 1 = RS-232, Port 2 = RS-485. Not software configurable in VersaMax or IC693CPU363; However, the specified value must be valid (0 or 1). 
#END#

Charac_Gap_Tmout
Character-gap time-out in 100-microsecond units. Range 0 - 65,535 (0 to 6.5535 seconds). This is the time interval that defines the end of each received response message. It is measured from the end of the last received character. RTS is off and the transmitter is silent during this interval. If a new query is ready for transmission, RTS is asserted no earlier than the end of this interval. On RS-485 ports, the Send Data and RTS signals remain in the high-impedance state until at least the end of this interval.
Zero specifies the default, defined as 3.5 character times at the specified data rate, assuming 11 bits per character.
*****************************************************************************************************************************************************************************************************
Data Rate 	Default (100 -sec. units) 	Data Rate 	Default (100 -sec. units)
*****************************************************************************************************************************************************************************************************
1200		322			19200		21
2400		161			38400		10
4800		80			57600		7
9600		40			115200		3
Any specified value smaller than the default is replaced by the default. This value also performs the function of the Modbus RTU slave receive-to-transmit delay. If the required delay is greater than the default value at the current data rate, increase the specified value to required delay in 100-microsecond units. If the required delay is less than the default at the current data rate, no additional delay is necessary.
#END#

RTS_Drop_Delay
RTS Drop Delay in 100 microsecond units: This is the time from the end the last transmitted character to the time when RTS is turned off (dropped). The receiver is disabled during transmission and remains disabled during the RTS drop delay time. If the specified delay is longer than the Modbus RTU slaves silent interval between the query and its response, the master will ignore all or part of the response. Zero specifies the default, defined as one character time at the specified data rate, assuming 11 bits per character. 
Data Rate 	Default (100 -sec. units) 	Data Rate 	Default (100 -sec. units)
1200		92			19200		6
2400		46			38400		3
4800		23			57600		2
9600		12			115200		1
Any specified value smaller than the default is replaced by the default. Note that RTS Drop Delay is specified in 10 millisecond units for Modbus RTU slave.
#END#

Slave_Device_ID
Slave device address
#END#
