Clock-Synchronous Serial I/O
Mitsubishi microcomputers
M16C / 62 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
334
In transmitting data in clock-synchronous serial I/O mode, choose functions from those listed in Table
2.4.1. Operations of the circled items are described below. Figure 2.4.7 shows the operation timing, and
Figures 2.4.8 and 2.4.9 show the set-up procedures.
2.4.2 Operation of Serial I/O (transmission in clock-synchronous serial I/O mode)
Note 1: This can be selected only when UART1 is used in combination with the internal clock. When this function is
_______ _______
selected, neither UART1 CTS/RTS function, nor UART0 CTS/RTS separation function can be utilized. Set the
_______ _______
UART1 CTS/RTS disable bit to “1”.
_______ _______
Note 2: UART0 only. (UART1 CTS/RTS function cannot be used when this function is selected.)
Note 3: UART2 only.
(1) Setting the transmit enable bit to “1” and writing transmission data to the UARTi transmit
buffer register makes data transmissible status ready.
________
_______
(2) When input to the CTSi pin goes to “L” level, transmission starts (the CTSi pin must be
controlled on the reception side).
(3) In synchronization with the first falling edge of the transfer clock, transmission data held in the
UARTi transmit buffer register is transmitted to the UARTi transmit register. At this time, the
UARTi transmit interrupt request bit goes to “1”. Also, the first bit of the transmission data is
transmitted from the TxDi pin. Then the data is transmitted bit by bit from the lower order in
synchronization with the falling edges.
(4) When transmission of 1-byte data is completed, the transmit register empty flag goes to “1”,
which indicates that transmission is completed. The transfer clock stops at “H” level.
(5) If the next transmission data is set in the UARTi transmit buffer register while transmission is
in progress (before the eighth bit has been transmitted), the data is transmitted in succession.
Operation
Item
Set-up
Transfer clock
source
CLK polarity
Internal clock (f1 / f8 / f32)
External clock (CLKi pin)
CTS function
CTS function enabled
CTS function disabled
Output transmission data at
the falling edge of the
transfer clock
Output transmission data at
the rising edge of the
transfer clock
O
Transmission
interrupt factor
Transmission buffer empty
Transmission complete
Output transfer clock
to multiple pins
(Note 1)
Not selected
Selected
CTS / RTS
separation function
(Note 2)
Pin shared by CTS and RTS
CTS and RTS separated
O
Transfer clock
LSB first
MSB first
O
Data logic select
function
(Note 3)
No reverse
Reverse
O
TXD, RXD I/O
polarity reverse bit
(Note 3)
No reverse
Reverse
O
Table 2.4.1. Choosed functions