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SWl
0
0
0
l
0
0
0
0
18
17
16
15
SW2
1
1
1
0
Last Character Received
Receive
Receive Data Buffer
Bit Buffer
Figure 17. Hardware Scan Block Diagram
Transmit
~fted
out by
Program
·Assuming that the transmit mode has been set, once each scan cycle a bit will be transmitted
from the bit buffer.
If
nothing is to be transmitted, the line should be in a marking condition
(idle).
Scan word 2 contains the character being transmitted. Upon the completion of trans-
mitting a character from scan word 2, the character in scan word 1 is transferred into scan
word 2, and automatically transmitted.
The program loads scan word 1 with the next character
to be transmitted.
PROGRAM INTERRUPT
Program interrupt occurs under control of the Q-counter. When Q counts to zero, the following
sequence occurs:
1.
The instruction being executed is completed. This can take from 1 to 10 (ten word times
is the *worst case execution time of the CSR instruction) word times, depending on
the instruction.
* See "Instruction Repertoire" for detailed description.
[ID/l\IJ/l\~~IY ~ ~@---------------
V-17
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