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Under
development
Preliminary Specifications REV.D
Specifications in this manual are tentative and subject to change.
Mitsubishi Microcomputers
M16C/80 group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
UARTi Special Mode Register
154
UARTi Special Mode Register (i = 2 to 4)
UART2 to UART4 operate the IIC bus interface (simple IIC bus) using the UARTi special mode register
(addresses 033616, 032616 and 02F616 [i = 2 to 4]) and UARTi special mode register 2 (addresses
033616, 032616 and 02F616 [i = 2 to 4]). UART3 and UART4 add special functions using UARTi special
mode resister 3 (addresses 032516 and 02F516 [i = 3 or 4]).
(1) IIC Bus Interface Mode
The I2C bus interface mode is provided with UART2 to UART4.
Table 1.20.1 shows the construction of the UARTi special mode register and UARTi special mode regis-
ter 2.
When the I2C mode select bit (bit 0 in addresses 033716, 032716 and 02F716) is set to “1”, the I2C bus
(simple I2C bus) interface circuit is enabled.
To use the I2C bus, set the SCLi and the SDAi of both master and slave to output with the function select
register. In UART3 and 4, set the data output select bit (bit 5 in address 032C16 and 02FC16) to N-channel
open drain output.
Table 1.20.1 shows the relationship of the IIC mode select bit to control. To use the chip in the clock
synchronized serial I/O mode or clock asynchronized serial I/O mode, always set this bit to “0”.
Function
Normal mode
I2C mode (Note 1)
Factor of interrupt number 33, 35, 37 (Note 2)
UARTi transmission
No acknowledgment detection (NACK)
Factor of interrupt number 34, 36, 38 (Note 2)
UARTi reception
Start condition detection or stop
condition detection
UARTi transmission output delay
Not delayed
Delayed
P70, P92, P96 at the time when UARTi is in use
TxDi (output)
SDAi (input/output) (Note 3)
P71, P91, P97 at the time when UARTi is in use
RxDi (input)
SCLi (input/output)
P72, P90, P95 at the time when UARTi is in use
CLKi
P72, P90, P95
DMA1 factor at the time when 1 1 0 1 is assigned
to the DMA request factor selection bits
UARTi reception
Acknowledgment detection (ACK)
Noise filter width
15ns
50ns
Reading P71, P91, P97
Reading the terminal when 0 is
assigned to the direction register
Reading the terminal regardless of the
value of the direction register
1
2
3
4
5
6
7
8
9
Note 1: Make the settings given below when I2C mode is in use.
Set 0 1 0 in bits 2, 1, 0 of the UARTi transmission/reception mode register.
Disable the RTS/CTS function. Choose the MSB First function.
Note 2: Follow the steps given below to switch from a factor to another.
1. Disable the interrupt of the corresponding number.
2. Switch from a factor to another.
3. Reset the interrupt request flag of the corresponding number.
4. Set an interrupt level of the corresponding number.
Note 3: Set an initial value of SDA transmission output when IIC mode (IIC mode select bit = "1") is valid and serial I/O is invalid.
Factor of interrupt number 39 to 41 (Note 2)
Bus collision detection
Acknowledgment detection (ACK)
10
Initial value of UARTi output
H level (when 0 is assigned to
the CLK polarity select bit)
The value set in latch P70, P92, P96
when the port is selected (Note 3)
11
Table 1.20.1. Features in I2C mode