Motorola PowerQUICC II MPC8280 Series Reference Manual page 809

Table 23-14 describes SCCS fields.
Bit Name
0–5 — Reserved, should be cleared.
6 CS Carrier sense (DPLL). Shows the real-time carrier sense of the line as determined by the DPLL.
0 The DPLL does not sense a carrier.
1 The DPLL senses a carrier.
7 — Reserved, should be cleared.
23.16 Programming the SCC BISYNC Controller
Software has two ways to handle data received by the BISYNC controller. The simplest is
to allocate single-byte receive buffers, request an interrupt on reception of each buffer, and
implement BISYNC protocol entirely in software on a byte-by-byte basis. This flexible
approach can be adapted to any BISYNC implementation. The obvious penalty is the
overhead caused by interrupts on each received character.
A more efficient method is to prepare and link multi-byte buffers in the RxBD table and use
software to analyze the first two to three bytes of the buffer to determine the type of block
received. When this is determined, reception continues without further software
intervention until it encounters a control character, which signifies the end of the block and
causes software to revert to byte-by-byte reception.
To accomplish this, set SCCM[RCH] to enable an interrupt on every received byte so
software can analyze each byte. After analyzing the initial characters of a block, either set
PSMR[RTR] or issue a
received, enter transparent mode. By setting the appropriate PSMR bit, the controller strips
the leading DLE from DLE-character sequences. Thus, control characters are recognized
only when they follow a DLE character. PSMR[RTR] should be cleared after a DLE-ETX
is received.
Alternatively, after an SOH is received, a
exclude SOH from BCS accumulation and reset the BCS. Notice that PSMR[RBCS] is not
needed because the controller automatically excludes SYNCs and leading DLEs.
After the type of block is recognized, SCCE[RCH] should be masked. The core does not
interrupt data reception until the end of the current block, which is indicated by the
reception of a control character matching the one in the receive control character table.
Using Table 23-15, the control character table should be set to recognize the end of the
block.
MOTOROLA
Freescale Semiconductor, Inc.
Table 23-14. SCCS Field Descriptions
RESET BCS CALCULATION
RESET BCS CALCULATION
Chapter 23. SCC BISYNC Mode
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Programming the SCC BISYNC Controller
Description
command. For example, if a DLE-STX is
should be issued to
23-17