MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 174

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

Communications Processor (CP)
character of 9 to 13 consecutive ones (if UM1–UM0 = 00) or by the address bit of the next
message (if UM0 = 1).
When the receiver is in sleep mode and a break sequence is received, the receiver will in-
crement the BRKEC counter and generate the BRK interrupt (if enabled).
4.5.11.11 UART Error-Handling Procedure
The UART controller reports character reception and transmission error conditions through
the channel BDs, the error counters, and the UART event register (SCCE). The modem in-
terface lines can also be monitored directly by the SCC status register.
Transmission Error
Reception Errors
4-54
Clear to Send Lost During Character Transmission. When this error occurs and the chan-
nel is not programmed to control this line with software, the channel terminates buffer
transmission, closes the buffer, sets the CTS lost (CT) bit in the BD, and generates the
TX interrupt (if enabled). The channel will resume transmission after the reception of the
RESTART TRANSMIT command.
1. Overrun Error. The UART controller maintains an internal three-byte FIFO for receiv-
2. Carrier Detect Lost During Character Reception. When this error occurs and the chan-
3. Framing Error. Framing error is reported by the UART controller when no stop bit is
4. Parity Error. When the parity error occurs, the channel writes the received character
5. Noise Error. Noise error is detected by the UART controller when the three samples
ing data. The CP begins programming the SDMA channel (if the data buffer is in ex-
ternal memory) when the first byte is received into the FIFO. When a receiver FIFO
overrun occurs, the channel writes the received character into the internal FIFO over
the previously received character (the previous character and its status bits are lost).
Then the channel writes the received character to the buffer, closes the buffer, sets
overrun (OV) in the BD, and generates the RX interrupt (if enabled). In automatic mul-
tidrop mode, the receiver enters hunt mode immediately.
nel is not programmed to control this line with software, the channel terminates char-
acter reception, closes the buffer, sets the carrier detect lost (CD) bit in the BD, and
generates the RX interrupt (if enabled). This error's priority is the highest; the last char-
acter in the buffer is lost and other errors are not checked. In automatic multidrop
mode, the receiver enters hunt mode immediately.
detected in a received data string. When this error occurs, the channel writes the re-
ceived character to the buffer, closes the buffer, sets framing error (FR) in the BD, and
generates the RX interrupt (if enabled). The channel also increments the framing error
counter (FRMEC). When this error occurs, parity is not checked for this character. In
automatic multidrop mode, the receiver enters hunt mode immediately.
to the buffer, closes the buffer, sets parity error (PR) in the BD, and generates the RX
interrupt (if enabled). The channel also increments the parity error counter (PAREC).
In automatic multidrop mode, the receiver enters hunt mode immediately.
taken on every bit are not identical. When this error occurs, the channel writes the re-
ceived character to the buffer and proceeds normally but increments the noise error
MC68302 USER’S MANUAL
MOTOROLA