Motorola MVME187 User Manual

Functional Description

2-19

All four serial ports use EIA-232-D drivers and receivers located on 
the MVME187, and all the signal lines are routed to the I/O 
connector. 

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Serial port 1 is a minimum function asynchronous port. It 
uses RXD, CTS, TXD, and RTS. 

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Serial ports 2 and 3 are full function asynchronous ports. 
They use RXD, CTS, DCD, TXD, RTS, and DTR. 

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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. 

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The MVME187 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.

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The interface provided by the PCCchip2 allows the 16-bit 
CD2401 to appear at contiguous addresses.

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Accesses to the CD2401 must be 8 or 16 bits: 32-bit accesses 
are not permitted. 

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The CD2401 supports DMA operations to local memory. 

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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. 

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The hardware does not restrict the CD2401 to onboard 
DRAM. 

Refer to the CD2401 data sheet for detailed programming 
information.