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The PCL-746+ is a four port serial communication interface card. Each
port can be configured individually to either RS-232, RS-422 or RS-485
using on-board jumpers.
The PCL-746+'s four 16C550 UARTs (on-chip 16-byte FIFO buffers)
make serial I/O more reliable. By buffering data into 16-byte packets
before putting it on the bus the UARTs drastically reduce the CPU
load. This makes the PCL-746+ especially suitable for high speed serial
I/O applications under MS Windows.
The PCL-746+ supports two operation modes: standard mode and
enhanced mode. In standard mode each of the four ports can be set up
individually as either the address or the IRQ channel. In enhanced
mode, all four ports can be set to share the same IRQ. When an on-
board interrupt occurs the interrupt status register indicates which
port has generated it. The shared interrupt can be set to most common
(extended ) AT interrupts. This simplifies programming, speeds up
interrupt processing and frees up interrupts for other devices.
In RS-485 mode, the PCL-746+ automatically senses the direction of
incoming data and switches its transmission direction accordingly.
Therefore no handshaking signal (e.g. RTS signal) is necessary. This
feature lets you simply and quickly build an RS-485 network with just
two wires. More importantly, application software previously written
for half duplex RS-232 environments, can be maintained without need
for modification.
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PCL-746+ User's Manual
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