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M16C/62P Group (M16C/62P, M16C/62PT)
17. Serial Interface
Rev.2.41
Jan 10, 2006
Page 205 of 390
REJ09B0185-0241
17.1.3
Special Mode 1 (I
2
C mode)
I
2
C mode is provided for use as a simplified I
2
C interface compatible mode. Table 17.10 lists the specifications
of the I
2
C mode. Table 17.11 to 17.12 lists the registers used in the I
2
C mode and the register values set. Table
13.13 lists the I
2
C Mode Functions. Figure 17.25 shows the block diagram for I
2
C mode. Figure 17.26 shows
Transfer to UiRB Register and Interrupt Timing.
As shown in Table 17.13, the microcomputer is placed in I
2
C mode by setting the SMD2 to SMD0 bits to
“010b” and the IICM bit to “1”. Because SDAi transmit output has a delay circuit attached, SDAi output does
not change state until SCLi goes low and remains stably low.
NOTES:
1. When an external clock is selected, the conditions must be met while the external clock is in the high state.
2. If an overrun error occurs, the value of UiRB register will be indeterminate. The IR bit in the SiRIC register does
not change.
Table 17.10
I
2
C Mode Specifications
Item
Specification
Transfer Data Format
Transfer data length: 8 bits
Transfer Clock
• During master
CKDIR bit in the UiMR (i=0 to 2) register = 0 (internal clock) : fj/ (2(n+1))
fj = f1SIO, f2SIO, f8SIO, f32SIO n: Setting value of UiBRG register 00h to FFh
• During slave
CKDIR bit = 1 (external clock) : Input from SCLi pin
Transmission Start
Condition
Before transmission can start, met the following requirements
(1)
• The TE bit in the UiC1 register= 1 (transmission enabled)
• The TI bit in the UiC1 register = 0 (data present in UiTB register)
Reception Start Condition
Before reception can start, met the following requirements
(1)
• The RE bit in UiC1 register= 1 (reception enabled)
• The TE bit in UiC1 register= 1 (transmission enabled)
• The TI bit in UiC1 register= 0 (data present in the UiTB register)
Interrupt Request
Generation Timing
When start or stop condition is detected, acknowledge undetected, and acknowledge
detected
Error Detection
Overrun error
(2)
This error occurs if the serial interface started receiving the next data before reading
the UiRB register and received the 8th bit of the next data
Select Function
• Arbitration lost
Timing at which the ABT bit in the UiRB register is updated can be selected
• SDAi digital delay
No digital delay or a delay of 2 to 8 UiBRG count source clock cycles selectable
• Clock phase setting
With or without clock delay selectable
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