HD6413008VF25 Datasheet, PDF (408/688 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

12. Serial Communication Interface
Figure 12.8 shows an example of SCI receive operation in asynchronous mode.
1
RDRF
FER
Start
bit
Data
Parity Stop Start
bit bit bit
Data
Parity Stop
bit bit
1
0 D0 D1
D7 0/1 1 0 D0 D1
D7 0/1 1
Idle (mark) state
1 frame
RXI interrupt
request
RXI interrupt handler
reads data in RDR and
clears RDRF flag to 0
Framing error,
ERI interrupt
request
Figure 12.8 Example of SCI Receive Operation
(8-Bit Data with Parity and One Stop Bit)
12.3.3 Multiprocessor Communication
The multiprocessor communication function enables several processors to share a single serial
communication line. The processors communicate in asynchronous mode using a format with an
additional multiprocessor bit (multiprocessor format).
In multiprocessor communication, each receiving processor is addressed by an ID. A serial
communication cycle consists of an ID-sending cycle that identifies the receiving processor, and a
data-sending cycle. The multiprocessor bit distinguishes ID-sending cycles from data-sending
cycles.
The transmitting processor starts by sending the ID of the receiving processor with which it wants
to communicate as data with the multiprocessor bit set to 1. Next the transmitting processor sends
transmit data with the multiprocessor bit cleared to 0.
Receiving processors skip incoming data until they receive data with the multiprocessor bit set to
1. When they receive data with the multiprocessor bit set to 1, receiving processors compare the
data with their IDs. Processors with IDs not matching the received data skip further incoming data
until they again receive data with the multiprocessor bit set to 1. Multiple processors can send and
receive data in this way.
Figure 12.9 shows an example of communication among different processors using a
multiprocessor format.
Rev.4.00 Aug. 20, 2007 Page 362 of 638
REJ09B0395-0400