7220 Datasheet, PDF (85/303 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

FUNCTIONAL DESCRIPTION
2.8 Multi-master I²C-BUS interface
2.8.3 START condition, STOP condition generation method
(1) START condition generation method
When the ESO bit of the I²C control register (address 00DA16) is “1,” execute a write instruction to
the I²C status register (address 00D916) to set the MST, TRX and BB bits to “1.” A START condition
will then be generated. After that, the bit counter becomes “0002” and an SCL for 1 byte is output.
The START condition generating timing and BB bit set timing are different in the standard clock mode
and the high-speed clock mode. Refer to “Figure 2.8.9” for the START condition generation timing
diagram, and “Table 2.8.2” for the START condition/STOP condition generation timing table.
(2) STOP condition generation method
When the ESO bit of the I²C control register (address 00DA16) is “1,” execute a write instruction to
the I²C status register (address 00D916) for setting the MST bit and the TRX bit to “1” and the BB
bit to “0”. A STOP condition will then be generated. The STOP condition generation timing and the
BB flag reset timing are different in the standard clock mode and the high-speed clock mode. Refer
to “Figure 2.8.10” for the STOP condition generating timing diagram, and “Table 2.8.2” for the
START condition/STOP condition generation timing table.
I²C status register
write signal
SCL
SDA
BB flag
Setup
time
Setup
time
Hold time
Set time for
BB flag
Fig. 2.8.9 START condition generation timing diagram
I²C status register
write signal
SCL
SDA
BB flag
Setup
time
Hold time
Reset time for
BB flag
Fig. 2.8.10 STOP condition generation timing diagram
Table 2.8.2 START condition/STOP condition generation timing table
Item
Standard clock mode
High-speed clock mode
Setup time
5.0 µ s (20 cycles)
2.5 µ s (10 cycles)
Hold time
5.0 µ s (20 cycles)
2.5 µ s (10 cycles)
Set/reset time for BB flag
3.0 µ s (12 cycles)
1.5 µ s (6 cycles)
Note: Absolute time at f = 4 MHz. The value in parentheses denotes the number of f cycles.
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7220 Group User’s Manual