MC68302EH20C Freescale Semiconductor, MC68302EH20C Datasheet - Page 207

• Manufacturer Part Number: MC68302EH20C
• Description: IC MPU MULTI-PROTOCOL 132-PQFP
• Manufacturer: Freescale Semiconductor

Specifications of MC68302EH20C

• Processor Type: M683xx 32-Bit
• Speed: 20MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 132-MQFP, 132-PQFP
• Family Name: M68000
• Device Core: ColdFire
• Device Core Size: 32b
• Frequency (max): 20MHz
• Instruction Set Architecture: RISC
• Supply Voltage 1 (typ): 5V
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 132
• Package Type: PQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Compliant

RESTART TRANSMIT Command
RESET BCS CALCULATION Command
ENTER HUNT MODE Command
4.5.13.5 BISYNC Control Character Recognition
The BISYNC controller can recognize special control characters. These characters are used
to “customize” the BISYNC protocol implemented by the BISYNC controller and may be
used to aid its operation in a DMA-oriented environment. Their main use is for receive buff-
ers longer than one byte. In single-byte buffers, each byte can easily be inspected, and con-
trol character recognition should be disabled.
MOTOROLA
mand may be used when it is necessary to abort transmission and transmit an EOT con-
trol sequence. The EOT sequence should be the first buffer presented to the BISYNC
controller for transmission after re-enabling transmission.
The STOP TRANSMIT command must be issued before the SCC mode register is used
to disable the transmitter if the transmitter is to be re-enabled at a later time.
The RESTART TRANSMIT command is used to begin or resume transmission from the
current Tx BD number (TBD#) in the channel's Tx BD table. When this command is re-
ceived by the channel, it will start polling the ready bit in this BD. This command is expect-
ed by the BISYNC controller after a STOP TRANSMIT command, after the STOP
TRANSMIT command and the disabling of the channel in its mode register, or after a
transmitter error (underrun or CTS lost) occurs.
If the transmitter is being re-enabled, the RESTART TRANSMIT command must be used
and should be followed by the enabling of the transmitter in the SCC mode register.
The RESET BCS CALCULATION command resets the receive BCS accumulator imme-
diately. For example, it may be used to reset the BCS after recognizing a control charac-
ter, signifying that a new block is commencing (such as SOH).
After a hardware or software reset and the enabling of the channel in the SCC mode reg-
ister, the channel is in the receive enable mode and will use the first BD in the table.
The ENTER HUNT MODE command is used to force the BISYNC controller to abort re-
ception of the current block, generate an RX interrupt (if enabled) as the buffer is closed,
and enter the hunt mode. In hunt mode, the BISYNC controller continually scans the input
data stream for the SYN1–SYN2 sequence as programmed in the data synchronization
register. After receiving the command, the current receive buffer is closed, and the BCS
is reset. Message reception continues using the next BD.
If an enabled receiver has been disabled (by clearing ENR in the SCC mode register), the
ENTER HUNT MODE command must be given to the channel before setting ENR again.
The BISYNC controller will remain in the transparent or normal
mode after receiving the STOP TRANSMIT or RESTART
TRANSMIT commands.
MC68302 USER’S MANUAL
NOTE
Communications Processor (CP)
4-87