HD6433045 HITACHI [Hitachi Semiconductor], HD6433045 Datasheet - Page 486

• Manufacturer Part Number: HD6433045
• Description: Hitachi Single-Chip Microcomputer
• Manufacturer: HITACHI [Hitachi Semiconductor]

Figure 13-8 shows an example of SCI receive operation in asynchronous mode.
13.3.3 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. The receiving processor with a matching ID continues to receive further
incoming data. 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 13-9 shows an example of communication among different processors using a
multiprocessor format.
Figure 13-8 Example of SCI Receive Operation (8-Bit Data with Parity and One Stop Bit)
RDRF
FER
1
Start
bit
0
D0
D1
1 frame
Data
D7
Parity
bit
0/1
Stop
bit
RXI
request
1
475
Start
bit
0
RXI interrupt handler
reads data in RDR and
clears RDRF flag to 0
D0
D1
Data
D7
Parity
bit
0/1
Framing error,
ERI request
Stop
bit
1
Idle (mark)
state
1