Motorola MVME167 Series Installation Manual page 41

All four serial ports use EIA-232-D drivers and receivers located on
the MVME167, and all the signal lines are routed to the I/O
connector.
Serial port 1 is a minimum function asynchronous port. It
uses RXD, CTS, TXD, and RTS.
Serial ports 2 and 3 are full function asynchronous ports.
They use RXD, CTS, DCD, TXD, RTS, and DTR.
Serial port 4 is a full function asynchronous or synchronous
port. It can operate at synchronous bit rates up to 64 k bits per
second. It uses RXD, CTS, DCD, TXD, RTS, and DTR. It also
interfaces to the synchronous clock signal lines.
Serial Interface Programming Considerations
The MVME167 board hardware ties the DTR signal from the
CD2401 to the pin labeled RTS at connector P2. Likewise, RTS
from the CD2401 is tied to DTR on P2. Therefore, when
programming the CD2401, assert DTR when you want RTS,
and RTS when you want DTR.
The interface provided by the PCCchip2 allows the 16-bit
CD2401 to appear at contiguous addresses
Accesses to the CD2401 must be 8 or 16 bits: 32-bit accesses
are not permitted.
The CD2401 supports DMA operations to local memory.
Because the CD2401 does not support a retry operation
necessary to break VMEbus lockup conditions, the CD2401
DMA controllers should not be programmed to access the
VMEbus.
The hardware does not restrict the CD2401 to onboard
DRAM.
Refer to the CD2401 data sheet for detailed programming
information.
Functional Description
2-19
2