MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 206

• Manufacturer Part Number: MC68000
• Manufacturer: MOTOROLA [Motorola, Inc]

Communications Processor (CP)
Memory Map for the placement of the three SCC parameter RAM areas and Table 4-5 for
the other parameter RAM values.
The M68000 core configures each SCC to operate in one of four protocols by the MODE1–
MODE0 bits in the SCC mode register. MODE1–MODE0 = 11 selects the BISYNC mode of
operation. The SYN1–SYN2 synchronization characters are programmed in the data syn-
chronization register (see 4.5.4 SCC Data Synchronization Register (DSR)).
The BISYNC controller uses the same basic data structure as the other protocol controllers.
Receive and transmit errors are reported through their respective BDs. The status of the line
is reflected in the SCC status register, and a maskable interrupt is generated upon each sta-
tus change.
There are two basic ways of handling the BISYNC channels. First, data may be inspected
on a per-byte basis, with the BISYNC controller interrupting the M68000 core upon receipt
of every byte of data. Second, the BISYNC controller may be operated so that software is
only necessary for handling the first two to three bytes of data; subsequent data (until the
end of the block) can be handled by the BISYNC controller without interrupting the M68000
core. See 4.5.13.14 Programming the BISYNC Controllers for more information.
4.5.13.4 BISYNC Command Set
The following commands are issued to the command register.
STOP TRANSMIT Command
4-86
SCC Base + 9C
SCC Base + 9E
SCC Base + A0 #
SCC Base + A2
SCC Base + A4 #
SCC Base + A6
SCC Base + A8
SCC Base + AA #
SCC Base + AC #
SCC Base + AE #
SCC Base + B0 #
SCC Base + B2 #
SCC Base + B4 #
SCC Base + B6 #
SCC Base + B8 #
SCC Base + BA #
SCC Base + BC #
SCC Base + BE #
After a hardware or software reset and the enabling of the channel using the SCC mode
register, the channel is in the transmit enable mode and starts polling the first BD in the
table approximately every eight transmit clocks.
The STOP TRANSMIT command aborts transmission after the contents of the FIFO are
transmitted (up to three bytes) without waiting until the end of the buffer is reached. The
TBD# is not advanced. SYNC characters consisting of SYNC-SYNC or DLE-SYNC pairs
(according to the transmitter mode) will be continually transmitted until transmission is re-
enabled by issuing the RESTART TRANSMIT command. The STOP TRANSMIT com-
# Initialized by the user (M68000 core).
Address
Table 4-9. BISYNC Specific Parameter RAM
CHARACTER2
CHARACTER3
CHARACTER4
CHARACTER5
CHARACTER6
CHARACTER7
CHARACTER8
CHARACTER1
PRCRC
PTCRC
BSYNC
PAREC
CRCC
TCRC
Name
RCRC
BDLE
RES
RES
MC68302 USER’S MANUAL
Width
Word
Word
Word
Word
Word
Word
Word
Word
Word
Word
Word
Word
Word
Word
Word
Word
Word
Word
Temp Receive CRC
CRC Constant
Preset Receiver CRC 16/LRC
Temp Transmit CRC
Preset Transmitter CRC 16/LRC
Reserved
Reserved
Receive Parity Error Counter
BISYNC SYNC Character
BISYNC DLE Character
CONTROL Character 1
CONTROL Character 2
CONTROL Character 3
CONTROL Character 4
CONTROL Character 5
CONTROL Character 6
CONTROL Character 7
CONTROL Character 8
Description
MOTOROLA