COTRUST CTH200 Series User Manual

Appendix
322
P Special Function Register
SMB0: System status bit
The 8 bits of SMB0 play a special role in the system. At the end of each scan cycle, the PLC will
update the 8 bits. Users can use the special functions of these bits in the program to achieve
some common operations, the details shows as following table:
SMB0 bit
Function description(read only)
SM0.0
The bit is always on and can be used as enable bit if you want a section of
a program to execute every cycle.
SM0.1
This bit is only 1 at first scan and can be used as the enable bit to initialize
segment.
SM0.2
If the power-off hold data is lost, the bit opens a scan cycle. This bit can be
used as an error memory bit or to activate enable bits in a particular startup
order.
SM0.3
When the power is turned on into RUN mode, the bit is switched on for a
scan cycle. And it can provide machine warm-up time before operation.
SM0.4
This bit offers a square wave clock pulse period 1 min, 30s on and 30s off.
SM0.5
This bit offers a square wave clock pulse period 1sec, 0.5s on and 0.5s off.
SM0.6
The bit is the scanning clock, set 1 for this scan and 0 for the next, which
also can be used as enable bit of scan counter.
SM0.7
This bit indicates PLC switch (0: TERM, 1: RUN) position, be used as the
enable bit of the FPORT communication program segment, when the
switch is at the RUN position, the FPORT communication mode is effective,
PPI communication is effective when switch to TERM.
SMB1: Instruction execution status bit
The 8 bits of SMB1 are used to indicate errors or special states in the execution of certain
instructions, as detailed in the following table:
SMB1 bit
Function description(read only)
SM1.0
Set 1 when instruction executed as 0
SM1.1
Set 1 when instruction execution results overflow or detect illegal value
SM1.2
Set 1 when instruction execution results is negative
SM1.3
Set 1 when the divisor in the instruction is 0
SM1.4
Set 1 if the appended table length exceeds the table range when executing
ATT instructions
SM1.5
Set 1 if the table is empty when executing a LIFO or FIFO instruction,
SM1.6
Set 1 when trying to convert a non-BCD number to a binary number
SM1.7
Set 1 When ASCII code cannot be converted to a valid hexadecimal
number
SMB2: FPORT receive character
SMB2 is the FPORT receive character buffer, every character received is put here under FPORT

COTRUST CTH200 Series Specifications

General

Brand	COTRUST
Model	CTH200 Series
Category	Controller
Language	English