Sundance SMT335E - Manual (Page 17)

Version 1.5 Page 17 of 53 SMT335E SMT375E User Manual
There is a control and status register for each of the six comm-ports. There is also
one read-only Global Comm-port Status Register that gathers status from all comm-
ports in one place.
Writing
The comm-port output buffer will be loaded with the first word written by the
C6000; the next 15 writes will fill up the output FIFO. When the FIFO is full
OFL will be 0 and OFF will be 1. Any further writes from the C6000 will be
discarded.
Reading
The 15 first words received will fill the input FIFO; the 16
th word received will
be kept in the comm-port input buffer. The C6000 can read up to 16 words;
any further read will return an indeterminate value.
Reset
CLRCP should only be used in special applications where the link’s token
exchange has been disabled. This will usually be where the other end of a link
is a device—not another comm-port—that will never attempt to change the
direction of transfer. Damage to the hardware could result if both ends of the
link end up as transmitters.
Clearing the comm-port
The control and status register can be used to discard words in the FIFOs.
Writing a value with CLROF or CLRIF set will clear the selected FIFO; there is
no need to set the bit back to zero.
Note that CLRIF and CLROF clear only the FIFOs; they do not clear the one-
word input or output buffers. On input you may need to set CLRIF twice. If the
FIFO is full and a word is in the input buffer, the first CLRIF will clear the FIFO
and allow a word to move in from the input buffer; the second CLRIF will
remove that word. On output you can only clear the output FIFO; any word
already in the output buffer can only be removed by being read from the other
end of the link.