MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
26-1
Chapter 26
SCC BISYNC Mode
The byte-oriented BISYNC protocol was developed by IBM for use in networking products. There are
three classes of BISYNC frames—transparent, nontransparent with header, and nontransparent without
header, shown in
Figure 26-1
. The transparent frame type in BISYNC is not related to transparent mode,
discussed in
Chapter 28, “SCC Transparent Mode.”
Transparent BISYNC mode allows full binary data to
be sent with any possible character pattern. Each class of frame starts with a standard two-octet
synchronization pattern and ends with a block check code (BCC). The end-of-text character (ETX) is used
to separate the text and BCC fields.
The bulk of a frame is divided into fields whose meaning depends on the frame type. The BCC is a 16-bit
CRC format if 8-bit characters are used; it is a combination longitudinal (sum check) and vertical (parity)
redundancy check if 7-bit characters are used. In transparent operation, a special character (DLE) is
defined that tells the receiver that the next character is text, allowing BISYNC control characters to be
valid text data in a frame. A DLE sent as data must be preceded by a DLE character. This is sometimes
called byte-stuffing. The physical layer of the BISYNC communications link must synchronize the
receiver and transmitter, usually by sending at least one pair of synchronization characters before each
frame.
BISYNC protocol is unusual in that a transmit underrun need not be an error. If an underrun occurs, a
synchronization pattern is sent until data is again ready. In nontransparent operation, the receiver discards
additional synchronization characters (SYNCs) as they are received. In transparent mode, DLE-SYNC
pairs are discarded. Normally, for proper transmission, an underrun must not occur between the DLE and
its following character. This failure mode cannot occur with the MPC885.
An SCC can be configured as a BISYNC controller to handle basic BISYNC protocol in normal and
transparent modes. The controller can work with the time-slot assigner (TSA) or nonmultiplexed serial
interface (NMSI). The SCC supports modem lines by connecting to port C pins or general-purpose I/O
pins. The controller has separate transmit and receive sections whose operations are asynchronous with the
core and either synchronous or asynchronous with other SCCs.
Nontransparent with Header
SYN1
SYN2
SOH
Header
STX
Text
ETX
BCC
Nontransparent without Header
SYN1
SYN2
STX
Text
ETX
BCC
Transparent
SYN1
SYN2
DLE
STX
Transparent
Text
DLE
ETX
BCC
Figure 26-1. Classes of BISYNC Frames
Содержание PowerQUICC MPC870
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Страница 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Страница 192: ...MPC885 Instruction Set MPC885 PowerQUICC Family Reference Manual Rev 2 5 22 Freescale Semiconductor ...
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Страница 416: ...External Bus Interface MPC885 PowerQUICC Family Reference Manual Rev 2 13 42 Freescale Semiconductor ...
Страница 440: ...Clocks and Power Control MPC885 PowerQUICC Family Reference Manual Rev 2 14 24 Freescale Semiconductor ...
Страница 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Страница 606: ...SDMA Channels and IDMA Emulation MPC885 PowerQUICC Family Reference Manual Rev 2 19 20 Freescale Semiconductor ...
Страница 738: ...SCC Asynchronous HDLC Mode and IrDA MPC885 PowerQUICC Family Reference Manual Rev 2 25 16 Freescale Semiconductor ...
Страница 780: ...SCC Ethernet Mode MPC885 PowerQUICC Family Reference Manual Rev 2 27 24 Freescale Semiconductor ...
Страница 794: ...SCC Transparent Mode MPC885 PowerQUICC Family Reference Manual Rev 2 28 14 Freescale Semiconductor ...
Страница 848: ...Serial Peripheral Interface SPI MPC885 PowerQUICC Family Reference Manual Rev 2 30 18 Freescale Semiconductor ...
Страница 882: ...Universal Serial Bus USB MPC885 PowerQUICC Family Reference Manual Rev 2 31 34 Freescale Semiconductor ...
Страница 944: ...Parallel I O Ports MPC885 PowerQUICC Family Reference Manual Rev 2 34 26 Freescale Semiconductor ...
Страница 956: ...CPM Interrupt Controller MPC885 PowerQUICC Family Reference Manual Rev 2 35 12 Freescale Semiconductor ...
Страница 1004: ...Buffer Descriptors and Connection Tables MPC885 PowerQUICC Family Reference Manual Rev 2 37 30 Freescale Semiconductor ...
Страница 1022: ...ATM Parameter RAM MPC885 PowerQUICC Family Reference Manual Rev 2 38 18 Freescale Semiconductor ...
Страница 1068: ...ATM Pace Control MPC885 PowerQUICC Family Reference Manual Rev 2 40 22 Freescale Semiconductor ...
Страница 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Страница 1120: ...AAL2 Implementation MPC885 PowerQUICC Family Reference Manual Rev 2 44 30 Freescale Semiconductor ...
Страница 1162: ...Fast Ethernet Controller FEC MPC885 PowerQUICC Family Reference Manual Rev 2 45 40 Freescale Semiconductor ...
Страница 1172: ...SEC Lite Overview MPC885 PowerQUICC Family Reference Manual Rev 2 46 8 Freescale Semiconductor ...
Страница 1176: ...SEC Lite Address Map MPC885 PowerQUICC Family Reference Manual Rev 2 47 4 Freescale Semiconductor ...
Страница 1214: ...SEC Lite Execution Units MPC885 PowerQUICC Family Reference Manual Rev 2 48 38 Freescale Semiconductor ...
Страница 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Страница 1313: ...MPC885 PowerQUICC Family Reference Manual Rev 2 Freescale Semiconductor B 1 Appendix B Serial Communications Performance TBD ...
Страница 1314: ...Serial Communications Performance MPC885 PowerQUICC Family Reference Manual Rev 2 B 2 Freescale Semiconductor ...
Страница 1320: ...Register Quick Reference Guide MPC885 PowerQUICC Family Reference Manual Rev 2 C 6 Freescale Semiconductor ...
Страница 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
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Страница 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Страница 1384: ...Serial ATM Scrambling Reception and SI Programming MPC885 PowerQUICC Family Reference Manual Rev 2 H 6 Freescale Semiconductor ...
Страница 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...