Manual

1–2 Overview of the CFM Module
Publication 17716.5.99 - December 1995
The rest of this chapter contains information on
CFM module operation.
Using the
CFM module
as a replacement for
a QRC module?
Y
N
Using the
CFM module
as replacement for
a QRD module?
Y
N
C
D
1
The CFM module performs high-speed totalizing and/or rate
calculation operations for various industrial applications. The CFM
module is a single-slot I/O module that interfaces between an
Allen-Bradley PLC processor that has block-transfer capability and
external I/O devices.
❷
External devices generate
input signals that are
transmitted to the
CFM module.
❸ The CFM module performs
calculations on
accumulated pulse
counts.
PLC5/40
processor
User Program
Data T able
1
The CFM module interfaces
with these PLC processors:
• PLC2 processor family
• PLC3 processor family
• PLC5

processor family
• PLC5/250

processors
1771CFM
❶ The PLC processor transfers your
configuration data and output channel
data to the CFM module using a block
transfer write (BTW) instruction.
❹ When instructed by your ladder program,
the PLC processor performs a block
transfer read (BTR) of the values
(count and/or frequency in binary format)
and stores them in a data table.
❺ The PLC processor and CFM module
determine that the transfer was made
without error.
❻ Your ladder program can use or
move the data before it is
written over by the transfer of
new data in a subsequent
transfer.
The CFM module interfaces with:
• magnetic pickup flowmeters
• 440V dc pulses (TTL compatible)
• proximity probes
BTW
BTR
What's Next
What the CFM Module
Does