M16C30L Datasheet, PDF (123/166 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

UART2 Special Mode Register
Mitsubishi microcomputers
M16C / 30L Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
UART2 Special Mode Register
The UART2 special mode register (address 037716) is used to control UART2 in various ways.
Figure 1.16.26 shows the UART2 special mode register.
Bit 0 of the UART2 special mode register (037716) is used as the I²C mode select bit.
Setting “1” in the I²C mode select bit (bit 0) goes the circuit to achieve the I²C bus (simplified I²C bus)
interface effective.
Table 1.16.9 shows the relation between the I²C mode select bit and respective control workings.
Since this function uses clock-synchronous serial I/O mode, set this bit to “0” in UART mode.
UART2 special mode register
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
U2SMR
Address
037716
When reset
8016
Bit
symbol
Bit
name
IICM ^{I2C mode select bit}
Function
(During clock synchronous
serial I/O mode)
Function
(During UART mode)
0 : Normal mode
1 : I²C mode
Must always be “0”
ABC Arbitration lost detecting 0 : Update per bit
flag control bit
1 : Update per byte
Must always be “0”
RW
BBS Bus busy flag
0 : STOP condition detected Must always be “0”
1 : START condition detected
(Note1)
LSYN SCL L sync output
enable bit
0 : Disabled
1 : Enabled
Must always be “0”
ABSCS ^{Bus collision detect}
Must always be “0”
sampling clock select bit
0 : Rising edge of transfer
clock
1 : Underflow signal of timer A0
ACSE
Auto clear function
select bit of transmit
enable bit
Must always be “0”
0 : No auto clear function
1 : Auto clear at occurrence of
bus collision
SSS
Transmit start condition Must always be “0”
select bit
0 : Ordinary
1 : Falling edge of RxD2
SDDS
SDA digital delay select
bit (Note 2)
0 : Must always be “0”
Must always be “0”
when not using I²C mode
1 : Digital delay output
is selected
Note 1: Nothing but “0” may be written.
Note 2: When not in I²C mode, do not set this bit by writing a “1”. During normal mode, fix it to “0”. When this
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”. Also, when SDDS = “0”, the U2SMR3 register cannot be
read or written to.
UART2 special mode register 3 (I²C bus exclusive use register)
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
U2SMR3
Address
037516
When reset
0016
Bit
symbol
Bit name
Function
(I² C bus exclusive use register)
Nothing is assigned.
In an attempt to write to these bits, write “0”. The value, if read, turns out to be
indeterminate. However, when SDDS = “1”, the value “0” is read out (Note 1)
RW
DL0
SDA digital delay setup b7 b6 b5
bit
(Note 1, Note 2, Note 3)
0 0 0 : Must not be set when using I²C mode
0 0 1 : 1 to 2 cycle(s) of 1/f(XIN)
DL1
0 1 0 : 2 to 3 cycles of 1/f(XIN)
0 1 1 : 3 to 4 cycles of 1/f(XIN)
Digital delay
1 0 0 : 4 to 5 cycles of 1/f(XIN)
is selected
DL2
1 0 1 : 5 to 6 cycles of 1/f(XIN)
1 1 0 : 6 to 7 cycles of 1/f(XIN)
1 1 1 : 7 to 8 cycles of 1/f(XIN)
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 UART2 special mode
register 3 (U2SMR3) after setting SDDS = “1”, be sure to write 0's 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”. After a reset, these bits are set to “000”. However,
because these bits can be read only when SDDS = “1”, the value read from these bits when SDDS = “0”
is indeterminate.
Note 3: 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 200 ns, so be sure to take this into account when using the device.
Figure 1.16.26. UART2 special mode register
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