Bus Status Register (Ibsr) - Fujitsu MB91150 Series Hardware Manual

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CHAPTER 16 I C INTERFACE

16.3.2 Bus Status Register (IBSR)

The bus status register (IBSR) has the following functions:
• Detection of repeated start conditions
• Detection of Arbitration Lost
• Acknowledge storage
• Data transfer
• Addressing detection
• Detection of general call address
• Detection of the first byte
I Bus status register (IBSR)
The bus status register (IBSR) has the following bit configuration:
Address
Bit7
0000_0121
BB
H
R
R: Read Only
[bit 7] BB (Bus Busy)
This bit indicates the I
0
1
[bit 6] RSC (Repeated Start Condition)
This bit is used to detect repeated start conditions.
0
1
If this bit is not addressed the INT bit is set to 0, or in slave mode, it is cleared by detection of
a start or stop condition when the bus is inactive.
[bit 5] AL (Arbitration Lost)
This bit is used to detect Arbitration Lost.
0
1
354
Bit6 Bit5 Bit4
RSC AL LRB
R R R
2
C bus status.
Stop condition is detected.
Start condition is detected (the bus is used).
Repeated start conditions are not detected.
Another start condition is detected while the bus is used.
Arbitration Lost is not detected.
Arbitration Lost occurred during transmission to or from the master, or the MSS
bit was set to 1 while another system is using the bus.
Bit3 Bit2 Bit1 Bit0
TRX AAS GCA FBT
R R R R
Initial value 00000000
B