
1-131
Under
development
Specifications in this manual are tentative and subject to change
Rev. H
UART2 in I2C Mode
MITSUBISHI MICROCOMPUTERS
M30222 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Fig. 1.104. UART2 special mode register
Symbol
Address
When reset
U2SMR3
037516
0016
UART2 Special mode register 3 (I2C and SPI bus exclusive use register)
DL0
DL1
DL2
0 : Normal mode
1 : SPI mode
Bit name
Bit symbol
b7
b6
b5
b4
b3
b2
b1
b0
SPIM
CPHA
SPI mode select bit
0 0 0 : Analog delay is selected
0 0 1 : 2 cycle of 1/f(X IN)
0 1 0 : 3 cycle of 1/f(X IN)
0 1 1 : 4 cycle of 1/f(X IN)
1 0 0 : 5 cycle of 1/f(X IN)
1 0 1 : 6 cycle of 1/f(X IN)
1 1 0 : 7 cycle of 1/f(X IN)
1 1 1 : 8 cycle of 1/f(X IN)
b7 b6 b5
W
R
SPI clock-phase
select bit
Function during clock
synchronous serial I/O mode
Function during
UART mode
0 : Data latched on
falling clock edge
1 : Data latched on
rising clock edge
Must always be "0'
Digital delay
is selected
SDA digital delay
set up bit (Note
1, 2, 3, 4, 5)
Nothing is assigned. In an attempt to write to these bits, write "0". When read the
value is indeterminate. However, when SDDS = "1", a "0" value is read.
_ _
Note 1:
This bit can be read or written to when UART2 special mode register U2SMR at address 037716 bit 7
(SDDS: SDA digital delay select bit) = "1". When the initial value of UART2 special mode register 3
(U2SMR3 is read after setting SDDS = "1", the value is "0016". When writing to U2SMR3 after setting
SDDS = "1", be sure to write 0s to bits 0 - 4. When SDDS = "0", This register cannot be written to;
when read, the value is indeterminate.
Note 2:
These bits are initialized to "000" when SDDS = "0", with the analog delay circuit selected. After a reset
these bits are set to "000", with the analog delay circuit selected. However, because these bits can be read
only when SDDS = "1", the value read from these bits when SDDS = "0" is indeterminate.
Note 3:
When analog delay is selected, only the analog delay value is effective; when digital delay is selected,
only the digital delay value is effective.
Note 4:
The amount of delay varies with the load on SCL and SDA pins. Also, when using an external clock,
the amount of delay increases by about 100ns. Be sure to take this into account when using this device.
Note 5:
Reset values for SPIM and CPHA are not affected by the state of SDDs. Their reset values are always "0".
(Note 1)
UART2 Special mode register
Symbol
Address
When reset
U2SMR
037716
0016
b7
b6
b5
b4
b3
b2
b1
b0
Bit name
Bit
symbol
W
R
Function
(During UART mode)
Function
(During clock synchronous
serial I/O mode)
ABSCS
ACSE
SSS
IIC mode selection bit
Bus busy flag
0 : STOP condition detected
1 : START condition detected
SCLL sync output
enable bit
Bus collision detect
sampling
clock select bit
Arbitration lost detecting
flag control bit
0 : Normal mode
1 : IIC mode
0 : Update per bit
1 : Update per byte
IICM
ABC
BBS
LSYN
0 : Ordinary
1 : Falling edge of RxD2
0 : Disabled
1 : Enabled
Transmit start condition
select bit
Must always be “0”
0 : Rising edge of transfer
clock
1 : Underflow signal of timer A0
Auto clear function
select bit of transmit
enable bit
0 : No auto clear function
1 : Auto clear at occurrence of
bus collision
Must always be “0”
Note 1: Nothing but "0" may be written.
Note 2: When not in I 2C mode, do not set this bit by writing a "1". During normal mode, fix it to "0". When this
(Note 1)
SDDS
SDA digital delay select
bit (Note 2, 3)
0 : Analog delay output is
selected
1 : Digital delay output is
selected (Must always
be "0" when not using
I2C mode)
Must always be "0"
bit - "0" , UART2 special mode register 3 (U2SMR3 at address 037516) bits 7 to 5 (DL2 to DL0 = SDA
digital delay setup bits) are initialized to "000", with the analog delay circuit selected. Also, when SDDS
= "0", the U2SMR3 register cannot be read or written to.
Note 3: When analog delay is selected, only the analog delay value is effective; when digital delay is selected
only the digital delay value is effective.