Serial Communication Controllers (SCCs)
7-164
MC68360 USER’S MANUAL
MOTOROLA
A—Address
This bit is valid only in multidrop mode (either automatic or non-automatic).
0 = This buffer contains data only.
1 = Set by the CPU32+ core, this bit indicates that this buffer contains address char-
acter(s). All the buffer’s data will be transmitted as address characters.
CM—Continuous Mode
0 = Normal operation.
1 = The R-bit is not cleared by the CP after this BD is closed, allowing the associated
data buffer to be retransmitted automatically when the CP next accesses this BD.
However, the R-bit will be cleared if an error occurs during transmission, regard-
less of the CM bit.
P—Preamble
0 = No preamble sequence is sent.
1 = The UART sends one character of all ones before sending the data so that the oth-
er end will detect an idle line before the data. If this bit is set and the data length of
this BD is zero, only a preamble will be sent.
NS—No Stop Bit Transmitted
0 = Normal operation. Stop bits are sent with all characters in this buffer.
1 = The data in this buffer will be sent without stop bits if the SYNC mode is selected
by setting the SYN bit in the PSMR. If ASYNC is selected the stop bit is SHAVED
according to the value of the DSR register.
The following bit is written by the CP after it has finished transmitting the associated
data buffer.
CT—CTS Lost
0 = The CTS signal remained asserted during transmission.
1 = The CTS signal was negated during transmission.
Data Length
The data length is the number of octets that the CP should transmit from this BD’s data
buffer. It is never modified by the CP. Normally, this value should be greater than zero.
The data length may be equal to zero with the P-bit set, and only a preamble will be sent.
Tx Data Buffer Pointer
The transmit buffer pointer, which always points to the first location of the associated data
buffer, may be even or odd. The buffer may reside in either internal or external memory.
7.10.16.18 UART EVENT REGISTER (SCCE).
The SCCE is called the UART event regis-
ter when the SCC is operating as a UART. It is a 16-bit register used to report events rec-
ognized by the UART channel and to generate interrupts. On recognition of an event, the
UART controller will set the corresponding bit in the UART event register. Interrupts gener-
ated by this register may be masked in the UART mask register. An example of interrupts
that may be generated by the UART is shown in Figure 7-49.