HD6417615 Hitachi Semiconductor, HD6417615 Datasheet - Page 607

• Manufacturer Part Number: HD6417615
• Description: Hardware Manual
• Manufacturer: Hitachi Semiconductor

14.3.3
The multiprocessor communication function performs serial communication using a
multiprocessor format, in which a multiprocessor bit is added to the transfer data, in asynchronous
mode. Use of this function enables data transfer to be performed among a number of processors
sharing a serial communication line.
When multiprocessor communication is carried out, each receiving station is addressed by a
unique ID code.
The serial communication cycle consists of two 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.
The transmitting station first sends the ID 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 stations skip the data until data with a 1 multiprocessor bit is sent. When data with a
1 multiprocessor bit is received, each receiving stations 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 the data until data with a 1 multiprocessor bit is again received. In this way, data
communication is carried out among a number of processors.
Figure 14.11 shows an example of inter-processor communication using a multiprocessor format.
594
Serial
data
RTS
Multiprocessor Communication Function
Figure 14.10 Example of Operation Using Modem Control (RTS)
Start
bit
0
D0
D1
D2
D7
Parity
bit
0/1
1
Start
bit
0