MOTOROLA
Chapter 25. SCC AppleTalk Mode
25-3
Part V. The Communications Processor Module
25.3 Connecting to AppleTalk
As shown in Figure 25-2, the MPC860 connects to LocalTalk, and, using TXD, RTS, and
RXD, is an interface for the RS-422 transceiver. The RS-422, in turn, is an interface for the
LocalTalk connector. Although it is not shown, a passive RC circuit is recommended
between the transceiver and connector.
Figure 25-2. Connecting the MPC860 to LocalTalk
The 16
´
overspeed of a 3.686-MHz clock can be generated from an external frequency
source or from one of the baud rate generators if the resulting output frequency is close to
a multiple of the 3.686 MHz frequency. The MPC860 asserts RTS throughout the duration
of the frame so that RTS can be used to enable the RS-422 transmit driver.
25.4 Programming the SCC in AppleTalk Mode
The AppleTalk controller is implemented by setting certain bits in the HDLC controller.
Otherwise, Chapter 24, ÒSCC HDLC Mode,Ó describes how to program the HDLC
controller. Use GSMR, PSMR, or TODR to program the AppleTalk controller.
25.4.1 Programming the GSMR
Program the GSMR as described below:
1. Set MODE to 0b0010 (AppleTalk).
2. Set DIAG to 0b00 for normal operation, with CD and CTS grounded or conÞgured
for parallel I/O. This causes CD and CTS to be internally asserted to the SCC.
3. Set RDCR and TDCR to (0b10) a 16
´
clock.
4. Set the TENC and RENC bits to 0b010 (FM0).
Two HDLC
CRC-16
Flags
Destination
Address
Data
Control
Byte
6-Bit Sync
Sequence
Source
Address
Closing
Flag
16 Ones
(Abort)
RS-422
TXD
RTS
RXD
Stored in Receive Buffer
Standard HDLC frame handling
MINI-DIN 8
Stored in Transmit Buffer
SCC
RTS
TXD
Tx Data
Tx Enable
Rx Data
MPC860
Connection
Summary of Contents for MPC860 PowerQUICC
Page 3: ...MPC860UM AD 07 98 REV 1 MPC860 PowerQUICC ª UserÕs Manual ...
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Page 78: ...I iv MPC860 PowerQUICC UserÕs Manual MOTOROLA Part I Overview ...
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Page 114: ...3 16 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part I Overview ...
Page 226: ...8 32 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part II PowerPC Microprocessor Module ...
Page 262: ...9 36 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part II PowerPC Microprocessor Module ...
Page 274: ...III iv MPC860 PowerQUICC UserÕs Manual MOTOROLA Part III Configuration ...
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Page 325: ...MOTOROLA Part IV Hardware Interface IV v Part IV Hardware Interface ...
Page 326: ...IV vi MPC860 PowerQUICC UserÕs Manual MOTOROLA Part IV Hardware Interface ...
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Page 632: ...21 44 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part V The Communications Processor Module ...
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Page 998: ...37 48 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part VI Debug and Test ...
Page 1016: ...A 10 MPC860 PowerQUICC UserÕs Manual MOTOROLA Appendixes ...
Page 1024: ...B 8 MPC860 PowerQUICC UserÕs Manual MOTOROLA Appendixes ...
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