Communication Blocks and Transaction Paths
The communication function blocks use one data transaction path and require multiple cycles to complete an operation. The number of transaction paths available by module and by MAST cycle depends on the communication port used:
Modbus Plus embedded port or NOM modules support up to 4 blocks at the same time.
TCP/IP Ethernet embedded port support up to 4 blocks at the same time.
TCP/IP Ethernet NOE, NOC, and 140 CRP 312 00 modules support up to 16 blocks at the same time.
More communication function blocks may be programmed on the same communication port. However, a communication block exceeding the maximum number on that port is not serviced until one of the transaction paths is available. Then, the next block on the same port becomes active and begins using an available path.
Available Communication Function on Low End CPUs
Communication function roles:
Function |
Role |
|---|---|
Continuously read a register area from a slave addressed via Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
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Continuously write a register area to a slave addressed via Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
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Perform various network communication operations on Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
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READ_REG (1) |
Read a register area from a slave addressed via Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
WRITE_REG (1) |
Write a register area to a slave addressed via Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
Modbus messages from master PLC and ASCII input/output strings. |
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(1) READ_REG and WRITE_REG communication functions are launched when an edge appears on the REG input. The communication is launched when REG is set to 1; then REG needs to be reset (0) and set to 1 again to launch the communication again. |
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Available Communication Function on High End CPUs
Communication function roles:
Function |
Role |
|---|---|
Continuously read a register area from a slave addressed via Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
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Continuously write a register area to a slave addressed via Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
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Perform data transfers through an EIO bus to and from Modbus slaves connected to a Modicon X80 rack |
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GET_TS_EVT_Q (2) |
Get the time stamped data in a Modicon BMX ERT 1604T or BMX CRA ••••• module in an EIO drop. |
Receive a character string from a Modicon X80 serial communication module through an EIO bus |
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Perform various network communication operations on Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
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Send a character string of 1000 bytes maximum from a Modicon X80 Modbus master through an EIO bus |
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READ_REG (1) |
Read a register area from a slave addressed via Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
Read registers in a Modbus slave connected to a Modicon X80 Modbus master through an EIO bus |
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READ_STS_QX (*) |
Read the status words of a Modicon X80 Ethernet I/O module by performing an explicit exchange with the processor memory |
WRITE_CMD_QX (*) |
Send a command to a Modicon X80 Ethernet I/O module with a command word by performing an explicit exchange |
WRITE_REG (1) |
Write a register area to a slave addressed via Modbus Plus, TCP/IP-Ethernet or SY/MAX-Ethernet |
Write registers in a Modbus slave connected to a Modicon X80 Modbus master through an EIO bus |
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Modbus messages from master PLC and ASCII input/output strings. |
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*: READ_STS_QX and WRITE_CMD_QX are part of the I/O Management Library (Explicit Exchange Family) 1: READ_REG and WRITE_REG communication functions are launched when an edge appears on the REG input. The communication is launched when REG is set to 1; then REG needs to be reset (0) and set to 1 again to launch the communication again. 2: GET_TS_EVT_Q is part of the System Library (SysClock family). |
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Utility Functions
Those functions are common to low end and high end CPUs and are synchronous functions. A function is said to be synchronous when it is completed during the CPU task that has activated it.
Communication function roles:
Function |
Role |
|---|---|
Convert a character string (respecting the Control Expert device address syntax) into an array of integers in order to manage Modicon X80 serial link modules in an Ethernet I/O drop |
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Convert a Modbus Plus address into an address that can be directly used by the communication functions |
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Convert a SYMAX/IP address into an address that can be directly used by the communication functions |
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Convert a TCP/IP address into an address that can be directly used by the communication functions |