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XC161 Derivatives
Peripheral Units (Vol. 2 of 2)
Asynchronous/Synchronous Serial Interface (ASC)
User’s Manual
18-19
V2.2, 2004-01
ASC_X, V2.0
18.3
Synchronous Operation
Synchronous Mode supports half-duplex communication, basically for simple I/O
expansion via shift registers. Data is transmitted and received via line RxD while line TxD
outputs the shift clock.
Synchronous Mode is selected with bitfield M = 000
B
.
Eight data bits are transmitted or received synchronous to a shift clock generated by the
internal baudrate generator. The shift clock is active only as long as data bits are
transmitted or received.
Figure 18-12 Synchronous Mode of Serial Channel ASC
Serial Port Control
MCA05443
13-bit Reload Register
13-bit Baudrate Timer
f
BRT
f
BR
f
DIV
MUX
2
3
R
f
ASC
Shift Clock
FIFO
Control
Shift Clock
TIR
TBIR
EIR
Receive Int.
Request
Transmit Buffer
Int. Request
M = 000
B
RIR
Transmit Int.
Request
Error Int.
Request
Receive FIFO Reg.
RBUF
Transmit FIFO Reg.
TBUF
Receive Shift
Register
Transmit Shift
Register
MUX
Internal Bus
BRS
OE
REN
OEN
LB
RxD
TxD
4
0
1