MOTOROLA
Chapter 26. SCC Asynchronous HDLC Mode and IrDA
26-5
Part V. The Communications Processor Module
26.7 Asynchronous HDLC Channel Implementation
The following points are speciÞc to asynchronous HDLC channel implementation:
¥
Flag sequenceÑThe transmitter automatically generates the opening and closing
ßags. The receiver removes opening and closing ßags before writing a frame to
memory and receives frames with only one shared ßag between frames, ignoring
multiple ßags.
¥
Address ÞeldÑThe address Þeld is neither generated nor examined by the
microcode while sending or receiving. The destination address Þeld of the frame
must be included in the Tx buffer. Any address Þeld compression, expansion, or
checking must be performed by the core.
¥
Control ÞeldÑThe control Þeld is neither generated nor examined by the microcode
during a transfer. The control Þeld of the frame must be included in the buffer. Any
control Þeld compression, expansion, or checking is done by the core.
¥
Frame check sequenceÑWhen sending, the frame check sequence (FCS) is
appended to the frame before the closing ßag is sent. The FCS is generated on the
original frame before transparency characters, start/stop bits, or ßags are added.
When receiving, the FCS is checked automatically and calculated after any
transparency characters, start/stop bits, and ßags are removed. For both, the
controller uses only a 16-bit CRC-CCITT polynomial.
¥
EncodingÑThe asynchronous HDLC controller supports 8 data bits, one start bit,
one stop bit, and no parity. Program PSMR[CHLN] to 0b11 for proper operation.
¥
Idle charactersÑWhen sending, the asynchronous HDLC controller sends idle
characters when no data is available; when receiving, it ignores idle characters.
26.8 Asynchronous HDLC Mode Parameter RAM
For asynchronous HDLC mode, the protocol-speciÞc area of the SCC parameter RAM is
mapped as in Table 26-1.
Table 26-1. Asynchronous HDLC-Specific SCC Parameter RAM Memory Map
Offset
1
Name
Width
Description
0x30
Ñ
Word
Reserved
0x34
C_MASK
Word
CRC constant. Initialize with 0x0000_F0B8.
0x38
C_PRES
Word
CRC preset. Initialize with 0x0000_FFFF.
0x3C
BOF
Hword Beginning-of-ßag-character. Initialize to PPP-0x7E, IrLAP - 0xC0.
0x3E
EOF
Hword End-of-ßag character. Initialize to PPP-0x7E, IrLAP-0xC1.
0x40
ESC
Hword Control escape character. Initialize to 0x7D for both PPP and IrLAP.
0x42
Ñ
Word
Reserved
0x46
ZERO
Hword Clear this Þeld.
Summary of Contents for MPC860 PowerQUICC
Page 3: ...MPC860UM AD 07 98 REV 1 MPC860 PowerQUICC ª UserÕs Manual ...
Page 36: ...xxxvi MPC860 PowerQUICC UserÕs Manual MOTOROLA CONTENTS Paragraph Number Title Page Number ...
Page 78: ...I iv MPC860 PowerQUICC UserÕs Manual MOTOROLA Part I Overview ...
Page 88: ...1 10 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part I Overview ...
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 ...
Page 320: ...12 12 MPC860 PowerQUICC UserÕs Manual MOTOROLA Part III Configuration ...
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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