
120
Rev. 1.0
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
with DATA ACQUISITION CONTROLLER
MITSUBISHI MICROCOMPUTERS
M306H2FCFP
2.11.5 UART2 Special Mode Register
The UART2 special mode register (address 037716) is used to control UART2 in various ways.
Figure 2.11.26 shows the UART2 special mode register.
Bit 0 of the UART special mode register (037716) is used as the I2C mode selection bit.
Setting “1” in the I2C mode select bit (bit 0) goes the circuit to achieve the I2C bus interface effective.
Since this function uses clock-synchronous serial I/O mode, set this bit to “0” in UART mode.
Figure 2.11.26 UART2 special mode register
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
I C 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 : I C 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”
Notes 1: Nothing but "0" may be written.
2: Do not write "1" except at I 2C mode. Must always be “0” at normal mode.
Bit 7 to bit5 (DL2 to DL0 = SDA digital delay value setting bit) of UART2 special mode
register 3 (U2SMR3/address 0375 16) are initialized and become “000” when this bit is "0", analog
delay circuit is selected. Reading and writing U2SMR are enable when SDDS = "0" .
3: Delaying ; Only analog delay value when analog delay is selected, and only digital delay value
when digital delay is selected.
(Note 1)
2
SDDS
SDA digital delay select
bit
(Notes 2 and 3)
0 : Selects analog delay
output
1 : Selects digital delay
output (Must always
be “0” except at I 2C
mode)
Must always be “0”
UART2 special mode register 3 (I2C bus exclusive register)
Symbol
Address
When reset
U2SMR3
037516
Indeterminate
b7
b6
b5
b4
b3
b2
b1
b0
Bit name
Bit
symbol
Function
(I2C bus exclusive)
SDA digital delay value
set bit
b7 b6 b5
DL0
DL1
DL2
(initializing value is "00 16" at SDDS = "1")
Nothing is assigned.
In an attempt to write to this bit, write “0”. The value, if read, turns out to be “0”.
“0” is read out when SDDS = 1.
W
R
Notes 1: Reading and writing is possible when bit7 (SDDS = SDA digital delay selection
bit) of UART2 special mode register (U2SMR/address 0377 16) is "1". When
set SDDS = "1" and read out initialized value of UART2 special mode register
3(U2SMR3), this value is "00 16".When set SDDS = "1" and write to UART2
special mode register 3(U2SMR3), set "0" to bit 0 to bit 4. When SDDS = "0",
writing is enable. When read out, this value is indeterminate.
2: When SDDS = "0" , this bit is initialized and become "000", selected analog
delay circuit. This bit is become "000" after end reset released, and selected
analog delay circuit. Reading out is possible when only SDDS = "1". when
SDDS = "0", value which was read out is indeterminate.
3: Delaying ; Only analog delay value when analog delay is selected, and only
digital delay value when digital delay is selected.
4: Delay level depends on SCL pin and SDA pin. And, when use external clock,
delay is increase around 100ns. So test first, and use this.
0 0 0 : Selects analog delay
0 0 1 : 1–2 cycle of 1/f (Xin)(Digital delay)
0 1 0 : 2–3 cycle of 1/f (Xin)(Digital delay)
0 1 1 : 3–4 cycle of 1/f (Xin)(Digital delay)
1 0 0 : 4–5 cycle of 1/f (Xin)(Digital delay)
1 0 1 : 5–6 cycle of 1/f (Xin)(Digital delay)
1 1 0 : 6–7 cycle of 1/f (Xin)(Digital delay)
1 1 1 : 7–8 cycle of 1/f (Xin)(Digital delay)