MC68HC812A4 Datasheet, PDF (250/342 Pages) Motorola, Inc – 16-bit device composed of standard on-chip peripheral modules connected by an intermodule bus. Modules include

Serial Communications Interface Module (SCI)
14.7.2 SCI Control Register 1
SCI0: $00C2
SCI1: $00CA
Bit 7
6
5
4
3
2
1
Bit 0
Read:
LOOPS WOMS RSRC
M
WAKE
ILT
PE
PT
Write:
Reset: 0
0
0
0
0
0
0
0
Figure 14-19. SCI Control Register 1 (SC0CR1 or SC1CR1)
Read: Anytime
Write: Anytime
LOOPS — Loop Select Bit
LOOPS enables loop operation. In loop operation the RXD pin is
disconnected from the SCI, and the transmitter output goes into the
receiver input. Both the transmitter and the receiver must be enabled
to use the loop function.
1 = Loop operation enabled
0 = Normal operation enabled
The receiver input is determined by the RSRC bit. The transmitter
output is controlled by the associated DDRS bit.
If the data direction bit for the TXD pin is set and LOOPS = 1, the
transmitter output appears on the TXD pin. If the DDRS bit is clear
and LOOPS = 1, the TXD pin is idle (high) if RSRC = 0 and
high-impedance if RSRC = 1. See Table 14-7.
WOMS — Wired-OR Mode Select Bit
WOMS configures the TXD and RXD pins for open-drain operation.
WOMS allows TXD pins to be tied together in a multiple-transmitter
system. Then the TXD pins of non-active transmitters follow the logic
level of an active 1. WOMS also affects the TXD and RXD pins when
they are general-purpose outputs. External pullup resistors are
necessary on open-drain outputs.
1 = TXD and RXD pins, open-drain when outputs
0 = TXD and RXD pins, full CMOS drive capability
MC68HC812A4 — Rev. 3.0
250
Serial Communications Interface Module (SCI)
Advance Information
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