Mitsubishi microcomputers
M16C / 6N0 / 6N1 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
155
Table 1.16.12. Specifications of S I/O3
Item
Transfer data format
Transfer clock
Conditions for
transmission/
reception start
Interrupt request
generation timing
Select function
Specifications
Transfer data length: 8 bits
With the internal clock selected (bit 6 at address 01E216 = "1"): fjSIO2/2(n+1)
(j = 2, 8, 32) (Note 1)
With the external clock selected (bit 6 at address 01E216 = "0"): Input from the CLK3
terminal (Note 2)
To start transmit/reception, the following requirements must be met:
- Select the synchronous clock (use bit 6 at address 01E216).
Select a frequency dividing ratio if the internal clock has been selected (use bits
0 and 1 at address 01E216).
- SOUT3 initial value set bit (use bit 7 at address 01E216) = "1".
- S I/O3 port select bit (bit 3 at address 01E216) = "1".
- Select the transfer direction (use bit 5 at address 01E216)
- Write transfer data to the S I/O3 transmit/receive register (address 01E016)
To use S I/O3 interrupts, the following requirements must be met:
- Clear the S I/O3 interrupt request bit (bit 3 at address 004916) before writing
transfer data to the S I/O3 transmit/receive register.
Rising edge of the last transfer clock. (Note 3)
LSB first or MSB first selection
Whether transmission/reception begins with bit 0 (LSB) or bit 7 (MSB) can be
selected.
Precaution
Unlike UART0 to 2, S I/O3 is not divided for transfer register and buffer.
Therefore, do not write the next transfer data to the S I/O3 transmit/receive
register (address 01E016) during a transfer.
When the internal clock is selected for the transfer clock, SOUT3 holds the last
data for a 1/2 transfer clock period after it finished transferring and then goes to a
high-impedance state. However, if the transfer data is written to the S I/O3
transmit/receive register (address 01E016) during this time, SOUT3 is placed in the
high-impedance state immediately upon writing and the data hold time is thereby
reduced.
Note 1: "n" is a value from 0016 to FF16 set in the S I/O3 transfer rate generator.
Note 2: With the external clock selected:
Before data can be written to the S I/O3 transmit/receive register (address 01E016), the CLK3 pin input
must be in the high state. Also, before rewriting bit 7 of the S I/O3 control register (address 01E216), make
sure the CLK3 pin input is held high.
The S I/O3 circuit keeps on with the shift operation as long as the synchronous clock is entered in it,
so stop the synchronous clock at the instant when it counts to eight. The internal clock, if selected,
automatically stops.
Note 3: If the internal clock is used for the synchronous clock, the transfer clock signal stops at the "H" state.
S I/O3