Renesas R5S72641 Manual Do Utilizador
Section 21 IEBus
TM
Controller
Page 1088 of 2108
R01UH0134EJ0400 Rev. 4.00
Sep
24,
2014
SH7262 Group, SH7264 Group
21.1.2
Communications Protocol
Figure 21.1 shows an IEBus transfer signal format.
Communications data is transferred as a series of signals referred to as a communications frame.
The number of data, which can be transmitted in a single communications frame and the transfer
speed, differs according to the communications mode.
The number of data, which can be transmitted in a single communications frame and the transfer
speed, differs according to the communications mode.
(When IEB
φ = 12, 18, 24, 30, or 36 MHz)
P
P A
P A
P A
P A
P A
1
Field name
Header
Master
address field
Slave address
field
Approximately 7330
μs
Approximately 2090
μs
Approximately 1590
μs
Approximately 1590
× N μs
Approximately 410
× N μs
Approximately 300
× N μs
Control field
Data field
Message
length field
Number
of bits
Transfer
time
Mode 0
Mode 1
Mode 2
Note: The value of acknowledge bit is ignored in broadcast communications.
P: Parity bit (1 bit)
A: Acknowledge bit (1 bit)
When A = 0: ACK
When A = 1: NAK
N: Number of bytes
A: Acknowledge bit (1 bit)
When A = 0: ACK
When A = 1: NAK
N: Number of bytes
1
Start
bit
Master
address
Slave
address
Control
bits
Data
bits
Data
bits
Message
length
bits
Broad-
cast
bit
1
1
1
4
8
1
1
8
1
1
8
1
1
1
1
12
12
Figure 21.1 Transfer Signal Format
(1) Header
A header is comprised of a start bit and a broadcast bit.
(a) Start Bit
The start bit is a signal to inform other units of the start of data transfer. A unit attempting to start
data transfer outputs a low-level signal (the start bit) for a specified period and then outputs the
broadcast bit.
data transfer outputs a low-level signal (the start bit) for a specified period and then outputs the
broadcast bit.
If another unit is already outputting a start bit when a unit attempts to output a start bit, the unit
waits for completion of the start bit from the other unit without outputting its own start bit, and
then outputs the broadcast bit synchronized with the completion timing.
waits for completion of the start bit from the other unit without outputting its own start bit, and
then outputs the broadcast bit synchronized with the completion timing.
Other units enter the receive state after detecting the start bit.