4. Functions
COM-1(PM), COM-1D(PM)
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4.
Functions
This section describes the functions of the PC Card.
Communication Function
Serial Data Transmission
COM-1(PM) sends and receives data using the RS-232C communication standard.
COM-1D(PM) sends and receives data using the RS-422A/485 communication standard.
The baud rate can be set by software to between 2 and 115,200bps.
RS-232C Control Lines (COM-1(PM))
All ports include the RTS, CTS, DTR, and DSR control lines.
The lines can be controlled or monitored by software from the application
RS-422A/485 Control Lines (COM-1D(PM))
All ports include the RTS+, RTS-, CTS+, and CTS- control lines.
The lines can be controlled or monitored by software from the application
Send and Receive Data Buffers
The card contains a 16byte send buffer and 16byte receive buffer.
The buffers operate as FIFO buffers and help reduce the load on the CPU for high-speed
communications or system operation.
The data buffer operation (whether to use FIFO operation, FIFO trigger size) can be set using Device
Manager (on Windows XP, 2000, Me, 98, and 95). On Windows NT, only whether to use FIFO
operation can be specified using [Control Panel] - [Serial Ports].
The FIFO trigger is the data buffer size that determines the timing of the hardware interrupt. However,
this setting and function only applies to the receive buffer and not to the send buffer.
Setting a large FIFO trigger size lightens the load on the CPU by reducing the number of hardware
interrupts generated by sending or receiving data.
However, as data is not actually sent or received until a certain amount is present, a delay may occur in
sending data to the other device or in notifying the application that data has been received.
Alternatively, setting a small FIFO trigger size or disabling FIFO operation increases the speed of data
sending and receiving but increases the load on the CPU and risks received data being missed.
As the FIFO buffer size is variable, you can adjust this setting to achieve optimum performance for your
system.
