68360 UART mode performance

68360 UART mode performance

Post by Trevor Dy » Thu, 24 Mar 1994 08:08:58

Hi there,

I have been using the UART mode of the SCCs on the '360 for a few weeks now.  I am finding that when I get to data rates of > 500 kbps or so, the RISC starts having problems keeping up with this quantity of data on the receive end.  (ie. I start getting frame errors or overrun errors).

The performance data in Appendix B of the 360 manual claims the UART mode is good up to 625 kbps.

Have you had any success/failure with higher rates??  Is there any performance difference between different SCCs?

Thanks kindly,



1. 68360 in UART mode

Two specific questions:

1 - I don't know in advance the length of packets received by the UART.
I think that what I'd like to do is interrupt after each character
is received, like a typical hardware UART.  Would I program the buffer
descriptor for a length of one byte.  Is there something clever I missed?

2 - The 68340 has an automatic RTS flow control on the receiver.
When the UART FIFO becomes nearly full, it negates RTS.  It would
surprise me if the 68360, with all it's features, did not have this
one, but I can't find it anywhere.

One general question:

The manual seems pretty good, and I intended to just dive in and
start programming.  But I got advice from one person recently that
this would be a disaster and that I should take a course from
Motorola first.  Opinions?

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