Arbitration - NEC 78K0R/KE3 User Manual

16-bit single-chip microcontrollers

Table of Contents

12.5.13 Arbitration

When several master devices simultaneously generate a start condition (when STT0 is set to 1 before STD0 is set

to 1), communication among the master devices is performed as the number of clocks are adjusted until the data

differs. This kind of operation is called arbitration.

When one of the master devices loses in arbitration, an arbitration loss flag (ALD0) in IIC status register 0 (IICS0)

is set (1) via the timing by which the arbitration loss occurred, and the SCL0 and SDA0 lines are both set to high

impedance, which releases the bus.

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 ALD0 = 1 setting that has been made by software.

For details of interrupt request timing, see 12.5.9

STD0: Bit 1 of IIC status register 0 (IICS0)

STT0: Bit 1 of IIC control register 0 (IICC0)

Transfer lines

CHAPTER 12 SERIAL INTERFACE IIC0

Interrupt request (INTIIC0) generation timing and wait

Figure 12-20. Arbitration Timing Example

User's Manual U17854EJ9V0UD

Master 1 loses arbitration