IDEC MicroSmart - Manual (Page 15)

1: G ENERAL I NFORMATION
« FC4A M ICRO S MART U SER ’ S M ANUAL » 1-3
Catch Input
Four inputs can be used as catch inputs. The catch input makes sure to receive short input pulses (rising pulse of 40 µs or
falling pulse of 150 µs minimum) from sensors without regard to the scan time.
Interrupt Input
Four inputs can be used as interrupt inputs. When a quick response to an external input is required, such as positioning
control, the interrupt input can call a subroutine to execute an interrupt program.
Timer Interrupt
In addition to the interrupt input, slim type CPU modules FC4A-D20RK1, FC4A-D20RS1, FC4A-D40K1, and FC4A-
D40S1 have a timer interrupt function. When a repetitive operation is required, the timer interrupt can be used to call a
subroutine repeatedly at predetermined intervals of 10 through 140 ms.
Input Filter
The input filter can be adjusted for eight inputs to reject input noises. Selectable input filter values to pass input signals are
0 ms, and 3 through 15 ms in 1-ms increments. The input filter rejects inputs shorter than the selected input filter value
minus 2 ms. This function is useful for eliminating input noises and chatter in limit switches.
User Program Read/Write Protection
The user program in the CPU module can be protected against reading and/or writing by including a password in the user
program. Read protection without a password is also available to inhibit reading completely.
Constant Scan Time
The scan time may vary whether basic and advanced instructions are executed or not depending on input conditions to
these instructions. When performing repetitive control, the scan time can be made constant by entering a required scan
time value into a special data register reserved for constant scan time.
Partial Program Download
Normally, the CPU module has to be stopped before downloading a user program. All CPU modules (except the all-in-one
10-I/O type) have run-time program download capabilities to download a user program containing small changes while the
CPU is running in either 1:1 or 1:N computer link system. This function is particularly useful to make small modifications
to the user program and confirm the changes while the CPU is running.
Analog Potentiometer
All CPU modules have an analog potentiometer, except the all-in-one 24-I/O type CPU module has two analog potentiom-
eters. The values (0 through 255) set with analog potentiometers 1 and 2 are stored to special data registers. The analog
potentiometer can be used to change the preset value for a timer or counter.
Analog Voltage Input
Every slim type CPU module has an analog voltage input connector. When an analog voltage of 0 through 10V DC is
applied to the analog voltage input connector, the signal is converted to a digital value of 0 through 255 and stored to a spe-
cial data register. The data is updated in every scan.
Pulse Output
Slim type CPU modules have pulse output instructions to generate high-speed pulse outputs from transistor output termi-
nals used for simple position control applications, illumination control, trapezoidal control, and zero-return control.
PID Control
All CPU modules (except the all-in-one 10- and 16-I/O types) have the PID instruction, which implements a PID (propor-
tional, integral, and derivative) algorithm with built-in auto tuning to determine PID parameters. This instruction is prima-
rily designed for use with an analog I/O module to read analog input data, and turns on and off a designated output to
perform PID control in applications such as temperature control. In addition, the PID instruction can also generate an ana-
log output using an analog I/O module.
Expansion Data Register
Slim type CPU modules FC4A-D20RK1, FC4A-D20RS1, FC4A-D40K3, and FC4A-D40S3 have expansion data registers
D2000 through D7999. Numerical data can be set to expansion data registers using
WindLDR . When downloading the user
program, the preset values of the expansion data registers are also downloaded to the EEPROM in the CPU module. Since
the data in the EEPROM is non-volatile, the preset values of the expansion data registers are maintained semi-permanently
and loaded to the RAM each time the CPU is powered up.