Serial Communications (16C452)
Signal Definitions
The following is a description of each of the 16C452 signal inputs and
outputs in the signal name. The 0 (zero) refers to serial port 1
(COM1) and the 1 (one) to serial port 2 (COM2).
Clear-To-Send Inputs (CTS0*, CTS1*)
The logical state of each CTS* pin is reflected in the CTS bit of the
Modem Status register (MSR), bit 4. A change of state in the CTS*
pin since the previous reading of the associated MSR in each serial
port causes the setting of the DCTS bit in the respective MSR, bit 0.
When CTS* is active (low), the modem is indicating that data on the
associated serial output (SOUT) can be transmitted.
Data-Set-Ready (DSR0*, DSR1*)
The logical state of the DSR* pins is reflected in the MSR, bit 5, of
the associated serial port. The DDSR bit, which is bit 1 in the MSR,
indicates whether the associated DSR* pin has changed state since the
previous reading of the MSR. When a DSR* pin is active (low), its
modem is indicating that it is ready to exchange data with the
associated UART.
8-11
