Mitsubishi microcomputers
M16C / 62 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Clock synchronous serial I/O mode
122
(1) Clock synchronous serial I/O mode
The clock synchronous serial I/O mode uses a transfer clock to transmit and receive data. Tables 1.19.2
and 1.19.3 list the specifications of the clock synchronous serial I/O mode. Figure 1.19.9 shows the
UARTi transmit/receive mode register.
Table 1.19.2. Specifications of clock synchronous serial I/O mode (1)
Item
Specification
Transfer data format
Transfer data length: 8 bits
Transfer clock
When internal clock is selected (bit 3 at addresses 03A016, 03A816, 037816
= “0”) : fi/ 2(n+1) (Note 1)
fi = f1, f8, f32
When external clock is selected (bit 3 at addresses 03A016, 03A816, 037816
= “1”) : Input from CLKi pin
Transmission/reception control
_______
CTS function/RTS function/CTS, RTS function chosen to be invalid
Transmission start condition
To start transmission, the following requirements must be met:
_ Transmit enable bit (bit 0 at addresses 03A516, 03AD16, 037D16) = “1”
_ Transmit buffer empty flag (bit 1 at addresses 03A516, 03AD16, 037D16) = “0”
_______
_ When CTS function selected, CTS input level = “L”
Furthermore, if external clock is selected, the following requirements must also be met:
_ CLKi polarity select bit (bit 6 at addresses 03A416, 03AC16, 037C16) = “0”:
CLKi input level = “H”
_ CLKi polarity select bit (bit 6 at addresses 03A416, 03AC16, 037C16) = “1”:
CLKi input level = “L”
Reception start condition
To start reception, the following requirements must be met:
_ Receive enable bit (bit 2 at addresses 03A516, 03AD16, 037D16) = “1”
_ Transmit enable bit (bit 0 at addresses 03A516, 03AD16, 037D16) = “1”
_ Transmit buffer empty flag (bit 1 at addresses 03A516, 03AD16, 037D16) = “0”
Furthermore, if external clock is selected, the following requirements must
also be met:
_ CLKi polarity select bit (bit 6 at addresses 03A416, 03AC16, 037C16) = “0”:
CLKi input level = “H”
_ CLKi polarity select bit (bit 6 at addresses 03A416, 03AC16, 037C16) = “1”:
CLKi input level = “L”
When transmitting
_ Transmit interrupt cause select bit (bits 0, 1 at address 03B016, bit 4 at
address 037D16) = “0”: Interrupts requested when data transfer from UARTi
transfer buffer register to UARTi transmit register is completed
_ Transmit interrupt cause select bit (bits 0, 1 at address 03B016, bit 4 at
address 037D16) = “1”: Interrupts requested when data transmission from
UARTi transfer register is completed
When receiving
_ Interrupts requested when data transfer from UARTi receive register to
UARTi receive buffer register is completed
Error detection
Overrun error (Note 2)
This error occurs when the next data is ready before contents of UARTi
receive buffer register are read out
Interrupt request
generation timing
Note 1: “n” denotes the value 0016 to FF16 that is set to the UART bit rate generator.
Note 2: If an overrun error occurs, the UARTi receive buffer will have the next data written in. Note also that
the UARTi receive interrupt request bit is not set to “1”.