IDEC MicroSmart - Manual (Page 279)

« FC4A M ICRO S MART U SER ’ S M ANUAL » 17-1
17: U
SER
C
OMMUNICATION
I
NSTRUCTIONS
Introduction
This chapter describes the user communication function for communication between the MicroSmart and external devices
with an RS232C port. The MicroSmart uses user communication instructions for transmitting and receiving communica-
tion to and from external devices.
Upgrade Information
Upgraded CPU modules of slim 20-I/O relay output types and 40-I/O types can also use the user communication through
the RS485 port and three additional BCC calculation formulas; ADD-2Comp, Modbus ASCII, and Modbus RTU. Applica-
ble CPU modules and system program version are shown in the table below. For the procedure to confirm the system pro-
gram version of the CPU module, see page 29-1.
Using the RS485 user communication, the MicroSmart CPU module can communicate with a maximum of 31 RS485
devices.
The upgraded CPU modules can use three new BCC calculation formulas of ADD-2comp, Modbus ASCII, and Modbus
RTU for transmit instructions TXD1 and TXD2 and receive instructions RXD1 and RXD2. Use
WindLDR ver. 4.40 or
higher to program the new BCC. For calculation examples, see page 17-36.
New BCC Calculation Formulas
User Communication Overview
The user communication mode is used for linking the MicroSmart to an RS232C communication device such as a com-
puter, modem, printer, or barcode reader.
The all-in-one 10-I/O type CPU module has one RS232C port. The 16- and 24-I/O type CPU modules have one RS232C
port and port 2 connector as standard. By installing an optional RS232C communication adapter (FC4A-PC1) to the port 2
connector, the 16- and 24-I/O type CPU modules can communicate with two external devices simultaneously.
Every slim type CPU module has one RS232C port. An optional RS232C communication module can be attached to any
slim type CPU module to use port 2 for additional RS232C communication. When an optional HMI base module is
attached to a slim type CPU module, an optional RS232C communication adapter can be installed to the port 2 connector
on the HMI base module.
User communication transmit and receive instructions can be programmed to match the communication protocol of the
equipment to communicate with. Possibility of communication using the user communication mode can be determined
referring to the user communication mode specifications described below.
CPU Module
All-in-One Type Slim Type
FC4A-C10R2
FC4A-C10R2C FC4A-C16R2
FC4A-C16R2C FC4A-C24R2
FC4A-C24R2C FC4A-D20K3
FC4A-D20S3
FC4A-D20RK1
FC4A-D20RS1
FC4A-D40K3
FC4A-D40S3
RS485 User Communication
Compatibility
— 204 or higher 204 or higher 204 or higher 202 or higher
User Communication BCC
Upgrade
(ADD-2Comp, Modbus ASCII,
and Modbus RTU)
BCC Name Description
ADD-2comp
Add the characters in the range from the BCC calculation star t position to the byte immediately before
the BCC, then inver t the result bit by bit, and add 1.
Modbus ASCII
Calculate the BCC using LRC (longitudinal redundancy check) for the range from the BCC calculation
star t position to the byte immediately before the BCC.
Modbus RTU
Calculate the BCC using CRC-16 (cyclic redundancy checksum) for the range from the BCC calculation
star t position to the byte immediately before the BCC. The generation polynomial is: X
16 + X 15 + X 2 + 1.