Arbitration; Arbitration Timing Example - NEC V850/SB1 User Manual

Slave Address
0000 000
0000 000
0000 001
0000 010
1111 0xx

10.3.10 Arbitration

When several master devices simultaneously output a start condition (when STTn is set to 1 before STDn is set to
Note
1 ), communication among the master devices is performed as the number of clocks is adjusted until the data
differs. This kind of operation is called arbitration (n = 0, 1).
When one of the master devices loses in arbitration, an arbitration loss flag (ALDn) in IIC status register n (IICSn)
is set at the timing by which the arbitration loss occurred, and the SCLn and SDAn lines are both set for high
impedance, which releases the bus (n = 0, 1).
The arbitration loss is detected based on the timing of the next interrupt request (the eighth or ninth clock, when a
stop condition is detected, etc.) and the ALDn = 1 setting that has been made by software (n = 0, 1).
For details of interrupt request timing, see 10.3.5 I
Note STDn: Bit 1 of IIC status register n (IICSn)
STTn: Bit 1 of IIC control register n (IICCn)
Master 1
SCL
SDA
Master 2
SCL
SDA
Transfer lines
SCL
SDA
Remark n = 0, 1
CHAPTER 10 SERIAL INTERFACE FUNCTION
Table 10-5. Extension Code Bit Definitions
R/W Bit
0 General call address
1 Start byte
X CBUS address
X Address that is reserved for a different bus format
X 10-bit slave address specification
2
C interrupt requests (INTIICn).
Figure 10-15. Arbitration Timing Example
User's Manual U13850EJ6V0UD
Description
Master 1 loses arbitration
Hi-Z
Hi-Z
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