Iebus Transfer Format - Renesas RZ/A Series User Manual

RZ/A1L Group, RZ/A1LU Group, RZ/A1LC Group
22.7.6

IEBus transfer format

Frame format
Remarks 1.
Figure 22-56 IEBus transfer signal format
R01UH0437EJ0600 Rev.6.00
Jan 29, 2021
The IEBus transfer signal format is shown in Figure 22-56.
Master
Header address
field
Master Slave
Broad-
Start
address address
cast P
bit
bit
bit
P: Parity bit
A: Acknowledge (ACK/NACK) bit
2. The master unit ignores the acknowledge bit during broadcast communication.
(1) Start bit
The start bit is a signal that informs the other units of the start of a data transfer.
The unit that is to start a data transfer outputs a low-level signal (start bit) for a specific
time, and then starts outputting the broadcast bit.
If another unit has already output its start bit when one unit is to output the start bit,
this unit does not output the start bit and instead waits for completion of output of the
start bit by the other unit. When the output of the start bit by the other unit is complete,
the unit starts outputting the broadcast bit in synchronization with the completion of
the start bit output by the other unit.
The units other than the one that started communication detect this start bit, and enter
the reception status.
(2) Broadcast bit
This bit indicates whether the master selects one slave (individual communication) or
multiple slaves (broadcast communication) as the other party of communication.
When the broadcast bit is 0, it indicates broadcast communication. When it is 1,
individual communication is indicated. Broadcast communication is classified into
two types: group-unit communication and all-unit communication. These
communication types are identified by the value of the slave address. (For the slave
address, see 22.7.6 (4) Slave address field.)
Because multiple slave units exist as a partner slave unit of communication in the case
of broadcast communication, the NACK signal is returned as an acknowledge bit in
each field subsequent to the master address field.
If multiple units start transmitting a communication frame at the same time, broadcast
communication takes precedence over individual communication, and wins in
arbitration.
If one unit occupies the bus as the master, the value set to the broadcast request flag
(the IEBBnBCR.IEBBnALRQ bit) is output.
Slave
Telegraph
address Control field length
field
field
Telegraph
Control
P A P A length
bit
bit
bit
22. IEBus Controller
Data field
Data Data
P A P A
bit bit
P A
22-114