SH7080 Datasheet, PDF (833/1644 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family

Section 15 Serial Communication Interface (SCI)
15.4.4 Multiprocessor Communication Function
Use of the multiprocessor communication function enables data transfer to be performed among a
number of processors sharing communication lines by means of asynchronous serial
communication using the multiprocessor format, in which a multiprocessor bit is added to the
transfer data. When multiprocessor communication is carried out, each receiving station is
addressed by a unique ID code. The serial communication cycle consists of two component cycles:
an ID transmission cycle which specifies the receiving station, and a data transmission cycle. The
multiprocessor bit is used to differentiate between the ID transmission cycle and the data
transmission cycle. If the multiprocessor bit is 1, the cycle is an ID transmission cycle, and if the
multiprocessor bit is 0, the cycle is a data transmission cycle. Figure 15.15 shows an example of
inter-processor communication using the multiprocessor format. The transmitting station first
sends the ID code of the receiving station with which it wants to perform serial communication as
data with a 1 multiprocessor bit added. It then sends transmit data as data with a 0 multiprocessor
bit added. The receiving station skips data until data with a 1 multiprocessor bit is sent. When data
with a 1 multiprocessor bit is received, the receiving station compares that data with its own ID.
The station whose ID matches then receives the data sent next. Stations whose ID does not match
continue to skip data until data with a 1 multiprocessor bit is again received.
The SCI uses the MPIE bit in SCSCR to implement this function. When the MPIE bit is set to 1,
transfer of receive data from SCRSR to SCRDR, error flag detection, and setting the SCSSR status
flags, RDRF, FER, and OER to 1 are inhibited until data with a 1 multiprocessor bit is received.
On reception of receive character with a 1 multiprocessor bit, the MPBR bit in SCSSR is set to 1
and the MPIE bit is automatically cleared, thus normal reception is resumed. If the RIE bit in
SCSCR is set to 1 at this time, an RXI interrupt is generated.
When the multiprocessor format is selected, the parity bit setting is invalid. All other bit settings
are the same as those in normal asynchronous mode. The clock used for multiprocessor
communication is the same as that in normal asynchronous mode.
Rev. 3.00 May 17, 2007 Page 775 of 1582
REJ09B0181-0300