Serial I/O (Special Modes)
162
Mitsubishi microcomputers
M16C / 62P Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
development
Preliminary Specifications Rev.1.0
Specifications in this manual are tentative and subject to change.
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 1.20.1 lists the speci-
fications of the I
2
C mode. Table 1.20.2 lists the registers used in the I
2
C mode and the register values
set. Figure 1.20.1 shows the block diagram for I
2
C mode. Figure 1.20.2 shows SCLi timing.
As shown in Table 1.20.3, the microcomputer is placed in I
2
C mode by setting the SMD2 to SMD0 bits to
‘010
2
’ 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.
Table 1.20.1. I
2
C Mode Specifications
Item
Transfer data format
Transfer clock
Specification
Transfer data length: 8 bits
During master
UiMR(i=0 to 2) register’s CKDIR bit = “0” (internal clock) : fj/ 2(n+1)
fj = f
1SIO
, f
2SIO
, f
8SIO
, f
32SIO
. n: Setting value of UiBRG register 00
16
to FF
16
During slave
CKDIR bit = “1” (external clock) : Input from CLKi pin
Before transmission can start, the following requirements must be met (Note 1)
_
The TE bit of UiC1 register= 1 (transmission enabled)
_
The TI bit of UiC1 register = 0 (data present in UiTB register)
Before reception can start, the following requirements must be met (Note 1)
_
The RE bit of UiC1 register= 1 (reception enabled)
_
The TE bit of UiC1 register= 1 (transmission enabled)
_
The TI bit of UiC1 register= 0 (data present in the UiTB register)
When start or stop condition is detected, acknowledge undetected, and acknowledge
detected
Overrun error (Note 2)
This error occurs if the serial I/O started receiving the next data before reading the
UiRB register and received the 8th bit of the next data
Arbitration lost
Timing at which the UiRB register’s ABT bit 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
Note 1: When an external clock is selected, the conditions must be met while the external clock is in the
high state.
Note 2: If an overrun error occurs, the value of UiRB register will be indeterminate. The IR bit of SiRIC
register does not change
.
Transmission start condition
Reception start condition
Error detection
Select function
Interrupt request
generation timing