User guide

112 DC 900-1338I
Protocol Software Toolkit Programmer Guide
transferring the received character from the SCC or IUSC receiver to the receive
data buffer, the interrupt service routine processes the character according to the
current state:
State 0 Search for start character. If the start character is found, move to state 1;
otherwise, take no action and ignore the current character (it will be over-
written by the next character).
State 1 Receive frame. Check for stop character. If the stop character is found and
CRC is enabled, move to state 2. If the stop character is found and CRC is
not enabled, process the end of received block and restart the receiver at
state 0 using the next buffer in the link-to-board queue. If the stop char-
acter is not found, store the character and increment the count.
State 2 First CRC byte. Move to state 3.
State 3 Second CRC byte. Process the end of received block and restart the
receiver at state 0 using the next buffer in the link-to-board queue.
SCC Special Receive Condition or IUSC Receive Status This interrupt is generated on
receiver overrun, parity error, or framing error. The appropriate error count is
incremented, but the receive is not aborted.
SCC or IUSC Transmit Buffer Empty This interrupt is generated on every transmitted
character. The transmit byte count is decremented, and the end of the transmis-
sion is processed if the count has reached zero. (The next transmission is started
at the task level.) The IUSC is set up to interrupt when there are 16 bytes free in
its transmit FIFO and up to 16 bytes are loaded during each interrupt.
6.3.3 ISR Operation in BSC Mode
In BSC mode, a simple header is prepended to the start of the data block, containing a
user-configured start character and a byte count. For transmit, the DMA transfer count