7480_M Datasheet, PDF (240/337 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER 740 FAMILY / 7470 SERIES

APPLICATIONS
2.3 Serial I/O
1 frame
1 byte
1 byte
1 byte
Max. 7 bytes
1 byte
1 byte
SOF Priority code Target ID Source ID
Data area
CRC code EOD RSP code EOF IFS
Transmit/Receive
Data Name
Function
SOF
Indicates the head of
(Start of Frame) _{the frame}
Transmission/Reception
• Fixed format of 6 time.
• Transmitter transmits ‘001111002’ with serial transmission.
• Receiver detects data with CNTR0 interrupt and recognizes with
pulse width measurement mode of timer X.
4 time 2 time
H
L
When transmitting
Priority
Code
Code for priority
control in multi-unit
transmission
• 1 bit represented by 3 time (1 byte represented by 3 bytes).
• Both transmitter and receiver communicate with serial I/O.
• Priority code: ‘0016’ (high priority) through ‘FF16’ (low priority).
Target ID
Source ID
Data Area
CRC Code
RSP Code
EOD
(End of Data)
ID number of
target unit
ID number of
transmit unit
Transmit data
3 time
H
L
Data
3 time
H
L
When transmitting ‘1’
3 time
H
L
When transmitting ‘0’
b7
1 byte data
b0
D7 D6 D5 D4 D3 D2 D1 D0
Transmit
data
generated
b7 ^{Transmit data 1} b0
D5 1 0 D6 1 0 D7 1
b7 ^{Transmit data 2} b0
1 0 D3 1 0 D4 1 0
Code for error
detection
Receiver transmits
self-address if data is
correctly received on
error detection
1 byte data transmit
Transmit data 1
H
L
b7 ^{Transmit data 3} b0
0 D0 1 0 D1 1 0 D2
Transmit data 2
Transmit data 3
D7
D6
D5
D4
D3
D2
D1
D0
Indicates the end of ^{• Fixed format of 3 time.}
data
• Both transmitter and receiver generate a wait time with timer 1.
EOF
Indicates the end of
(End of Frame) _frame
IFS
(Inter-Frame
Separation)
Indicates the
separation between
frames
3 time
H
L
• Fixed format of 6 time.
• Both transmitter and receiver generate a wait time with timer 1.
6 time
H
L
Figure 2.3.11 Communication Format Example of Simplified SAE J1850
7480 Group and 7481 Group User's Manual
2-25