MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 177

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

FRZ—Freeze Transmission
CL—Character Length
RTSM—RTS Mode
SL—Stop Length
COMMON SCC MODE BITS—see 4.5.3 SCC Mode Register (SCM) for a description of the
DIAG1, DIAG0, ENR, ENT, MODE1, and MODE0 bits.
4.5.11.14 UART Receive Buffer Descriptor (Rx BD)
The CP reports information about each buffer of received data by its BDs. The Rx BD is
shown in Figure 4-20. The CP closes the current buffer, generates a maskable interrupt, and
starts to receive data in the next buffer due to any of the following events:
MOTOROLA
This bit allows the user to halt the UART transmitter and to continue transmission from the
next character in the buffer at a later time.
This bit selects the number of the stop bits transmitted by the UART. The receiver is al-
ways enabled for one stop bit. Fractional stop bits are configured in the DSR (see
4.5.11.12 Fractional Stop Bits).
1. Reception of a user-defined control character (when reject (R) bit = 0)
2. Detection of an error during message processing
3. Detection of a full receive buffer
4. Reception of a programmable number of consecutive IDLE characters
10 = The DDCMP protocol is implemented over the asynchronous channel.
11 = Multidrop mode is enabled as in the 01 case, and the IMP automatically checks
0 = Normal operation (or resume transmission after FRZ is set).
1 = The UART completes transmission of any data already transferred to the UART
0 = 7-bit character length. On receive, bit 7 in memory is written as zero. On transmit,
1 = 8-bit character length
0 = RTS is asserted whenever the transmitter is enabled and there are characters to
1 = RTS is asserted whenever the transmitter is enabled (the ENT bit is set).
0 = One stop bit
1 = Two stop bits
FIFO (up to three characters) and then stops transmitting data. The UART contin-
ues to receive normally.
bit 7 in memory is a don't care.
transmit. RTS is negated after the last stop bit of a transmitted character when both
the shift register and the transmit FIFO are empty. RTS is also negated at the end
of a buffer to guarantee accurate reporting of the CTS bit in the BD.
ceives the address character and writes it to a new buffer. No address recognition
is performed.
the address of the incoming address character and either accepts or discards the
data following the address.
MC68302 USER’S MANUAL
Communications Processor (CP)
4-57