Determination Of Bus Mastership (Arbitration); Communication Mode - Renesas RZ/A Series User Manual

RZ/A1L Group, RZ/A1LU Group, RZ/A1LC Group
22.7.2

Determination of bus mastership (arbitration)

Caution
22.7.3

Communication mode

R01UH0437EJ0600 Rev.6.00
Jan 29, 2021
An operation to occupy the bus is performed when a unit connected to the IEBus
controls the other units. This operation is called arbitration.
When multiple units simultaneously start transmission, arbitration is used to grant one
of the units permission to occupy the bus.
Because only one unit is granted bus mastership as a result of arbitration, the priority
conditions of the bus are predetermined as follows.
Bus mastership is canceled if communication is aborted.
(1) Priority by communication type
Broadcast communication (communication from one unit to multiple units) takes
precedence over normal communication (communication from one unit to another).
(2) Priority by master address
If the communication type is the same, communication with the lower master address
takes precedence.
A master address consists of 12 bits, with unit 000H having the highest priority and
unit FFFH having the lowest priority.
The IEBus has three communication modes, each of which has a different transfer rate.
This module supports communication modes 1 and 2. The transfer rate and the
maximum number of transfer bytes per communication frame in communication
modes 1 and 2 are shown below.
Table 22-56 Transfer rate and maximum number of transfer bytes in
each communication mode
Communication mode
1
2
a)
Effective transfer rate when the maximum number of transfer bytes is transmitted
Select the communication mode for each unit connected to the IEBus before starting
communication. If the communication mode of the master unit and that of the partner
unit (slave unit) are not the same, communication is not correctly executed.
Maximum number of
transfer bytes
(bytes/frame)
32 bytes/frame
128 bytes/frame
22. IEBus Controller
a
Effective transfer rate
Approx. 18 kbps
Approx. 27 kbps
22-112