Micromod MOD: 1800P - MOD 30ML Identity Module (Version 2) System, I/O and Communications Functions - Manual (Page 99)

Logic Functions - Book 1
MODCELL SERIAL COMMUNICATION BLOCK
4-17
4.3 MODCELL SERIAL COMMUNICATION BLOCK (MSC)
The Modcell Serial communication (MSC) block supports Modbus Slave, Extended Modbus
Slave or Modbus Master communications over either a point-to-point or point-to-multipoint
network. This block supports the Modbus Remote Terminal Unit (RTU) mode of transmission.
The ASCII mode is not supported.
A functional block diagram of the block is shown in Figure 4-6. The MSC block Application
Builder displays which are used to configure the block are shown in Figure 4-7 (page 1) and
Figure 4-8 (page 2). List connections are made to the MSC block.
Modbus Slave
Modbus Slave communications can only be used for reading and writing MODCELL attributes
as registers or coils. This is accomplished by attaching configured lists (CL) and Modbus lists
(ML) to the Discrete Read/Write Lists, Discrete Read Only Lists, Single Register Read/Write
Lists, Single Read Only Lists, Multiple Read/Write Lists and Multiple Read Only Lists. A
Modbus Reference File (MRF) is created for each MSC block in the database. The reference
file contains all configured lists and Modbus lists referenced in the MSC block. For each
referenced list, the file includes all of the points (or registers), LSPs, data types, and any range
or scale factors.
Extended Modbus Slave
The Extended Modbus protocol can be used to access everything within Modcell such as data
base downloading, reading diagnostics, reading the system event queue and reading and
writing attributes. Attaching a Configured List (CL) to this block’s Foreground List attribute will
allow Modcell data to be gathered and packed the same as used in the ICN communication
block. To take advantage of these features, the master’s communication driver must be
appropriately modified. Contact
MicroMod Automation for Extended Modbus protocol info.
Modbus Master
This block can be used as a Modbus Master to any Modbus compatible devices. See
Appendix B, Modbus Master Configuration for details.
Communication Modules
One MSC block can support one RS485 (one or two slots) or one RS232 (two slots)
Communication module. Each MSC occurrence is associated with the port of the same
number. MSC1 is configured as port number one (slots 32 or 31-32) on the I/O Module Block
Selection display in the configurator; MSC2 is port two (slots 29 or 28-29, or 30 or 29-30); and
MSC3 is port three (slots 26 or 25-26, 27 or 26-27, or 28 or 27-28).
RS232 modules support point-to-point networks. RS485 modules support either point-to-point
or point-to-multipoint networks. The RS485 and the RS232 module with address switches
support Extended Modbus. When an RS485 communication bus is being used, the Modbus
Master is responsible for providing pull-up and pull-down resistors which will keep the bus in a
MARK/IDLE state when all the transmitters are tri-stated. Refer to IB-23C600, Issue 5 or later
for connection information.