H3 -1
Chapter 3 Expansion of FB
S
-PLC
If the I/O point of the. Main unit of the applied FB
S
-PLC is not enough for a specific application, then can expand it with
the additional expansion units/modules. Besides I/O point there also have the requirements to expand the
communication port in some occasions.
3.1
I/O Expansion
The expansion of FB
S
-PLC I/O consists of Digital I/O ( DI/O, which status is represented by a single bit) and the Numeric
I/O (NI/O , which status is represented by a 16-bit Word). Either the DI/O or the NI/O expansion is realized through
expansion units or modules cascaded thru the usage of the “I/O Output Expansion Connector” located at the right side of
FB
S
-PLC or expansion unit/ module.
The I/O points of FB
S
-PLC system are limited to 512 points of DI/O (256 points for DI and DO, respectively), 128 words
of NI/O (64 words for NI and NO, respectively). Besides this there are two limits imposed by hardware:
○
1 . A maximum
number of 32 units or modules can be used in the expansion.
○
2 . The total length of the expansion cables cannot
exceed 5 meters.
Note
1. If the I/O points of the application system exceed one of the limitations(256 DI,256 DO,64 NI, 64 NO), while
startup the main unit of FB
S
-PLC will treat this as an illegal I/O configuration, which in return will flag as an error
situation by turn on the “ERR” LED and put the error code in Y0~Y3 LED(refer the page 8-2, Chapter 8). The
corresponding error code will also be indicated in the CPU status register (R4049).
2. The maximum number of expansion units/modules of FB
S
-PLC is 32. Beyond this numbers will be treated as
an invalid I/O configuration and the main unit will stop its operation, which in return will flag as an error situation
by turn on the “ERR” LED and put the error code in Y0~Y3 LED(refer the page 8-2, Chapter 8). The
corresponding error code will also be indicated in the CPU status register (R4049).
Warning
1. The maximum length of the I/O expansion cable for FB
S
-PLC is 5 meters. Cables longer than that will cause
incorrect I/O operation because of excess signal delay in hardware or noise pickup, resulting in damage to
equipment or posing hazard to operating personnel. Since this kind of situation cannot be detected by the PLC
main unit, users are advised to take extra cautions and necessary measures.
3.1.1
Digital I/O Expansion and I/O Numbering
Digital I/O means I/O with the discrete type status, including digital input (with initial X in DI numbering) and digital
output (with initial with Y in DO numbering). The DI and DO of FB
S
-PLC can both be expanded up to 256 points
(numbered as X0~X255 and Y0~Y255, each with 256 points).
The status of input contacts (X0~X255) of PLC come from the input signal connected to the digital input terminal block
on main unit or expansion unit/module; while the status appears at digital output terminal block of main unit and
expansion unit/module reflects the digital output relay (Y0~Y255) status inside PLC.
On FBs-PLC main unit, at the position below the digital input terminal block and the position above the output terminal
block, there have labels indicate the corresponding signal name. They label each terminal with numbers representing
the corresponding digital input contact Xn and digital output relay Yn. In the example of the main unit in FB
S-
24MC, the
corresponding digital input contacts on the input terminal block are labeled X0~13, and the corresponding digital output
relays on the output terminal block Y0~Y9. Users only need to locate the printed label for each terminal to find out its
I/O number. The LED status display region also indicates the ON/OFF status for all DI(X0~X13) and DO(Y0~Y9) on the
