Sundance SMT335E - Manual (Page 18)

Version 1.5 Page 18 of 53 SMT335E SMT375E User Manual
Interrupts:
The comm-port control logic can assert an interrupt condition as the result of
data being transferred. The condition indicates that either one word or a block
of 8 words has been moved. The bits IFBM and OFBM in the comm-port
control and status register select which condition will assert the interrupt line.
IFBM controls interrupt conditions for input and OFBM for output.
If IFBM=0, the condition will be asserted whenever IFE=0.
If IFBM=1, the condition will be asserted as soon as the input FIFO contains at
least 8 words. The condition will not be asserted again, even if the FIFO
contains 8 or more words, until either of the following events has occurred:
• 8 words have been read from the input FIFO; or
• A write to an interrupt control register (ICR) has set the associated
Interrupt Enable.
Following one of these events, the condition will be asserted again if or as
soon as the input FIFO contains at least 8 words.
If OFBM=0, the condition will be asserted whenever OFF=0.
If OFBM=1, the condition will be asserted as soon as the output FIFO has
space for 8 or more words. The condition will not be asserted again, even if
the FIFO has space for 8 or more words, until either of the following events
has occurred:
• 8 words have been written to the output FIFO; or
• A write to an interrupt control register (ICR) has set the associated
Interrupt Enable.
Following one of these events, the condition will be asserted again if or as
soon as the output FIFO contains space for at least 8 words.
Transfer techniques
Transfers can be managed using polling or interrupts, each with CPU control
or DMA. The distribution disk provides programs that demonstrate transfers
and indicate the transfer speeds achieved using these four techniques.