Mitsubishi microcomputers
M16C / 61 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Serial I/O
87
Serial I/O
Serial I/O is configured as three channels: UART0, UART1 and UART2. UART0, UART1 and UART2 each
have an exclusive timer to generate a transfer clock, so they operate independently of each other.
Figure 1.17.1 shows the block diagram of UART0, UART1 and UART2. Figure 1.17.2 and figure 1.17.3
show the block diagram of the transmit/receive unit.
UARTi (i = 0 to 2) has two operation modes: a clock synchronous serial I/O mode and a clock asynchronous
serial I/O mode (UART mode). The contents of the serial I/O mode select bits (bits 0 to 2 at addresses
03A0
16
, 03A8
16
and 0378
16
) determine whether UARTi is used as a clock synchronous serial I/O or as a
UART.
UART0 through UART2 are almost equal in their functions with minor exceptions. UART2, in particular, is
compliant with the SIM interface with some extra settings added in clock-asynchronous serial I/O mode
(Note). It also has the bus collision detection function that generates an interrupt request if the T
X
D pin and
the R
X
D pin are different in level.
Note: SIM : Subscriber Identity Module
Table 1.17.1 shows the comparison of functions of UART0 through UART2, and Figures 1.17.4 through
1.17.8 show the registers related to UARTi.
Note 1: Only when clock synchronous serial I/O mode.
Note 2: Only when clock synchronous serial I/O mode and 8-bit UART mode.
Note 3: Only when UART mode.
Note 4: Using for SIM interface.
UART0
UART1
UART2
Function
CLK polarity selection
Continuous receive mode selection
LSB first / MSB first selection
Impossible
Transfer clock output from multiple
pins selection
Impossible
Impossible
Impossible
Impossible
Serial data logic switch
Impossible
Sleep mode selection
Impossible
Impossible
TxD, RxD I/O polarity switch
Impossible
Possible
CMOS output
TxD, RxD port output format
CMOS output
N-channel open-drain
output
Impossible
Parity error signal output
Impossible
Impossible
Bus collision detection
Impossible
Possible
Possible
(Note 1)
Separate CTS/RTS pins
Possible
(Note 1)
Possible
(Note 1)
Possible
(Note 3)
Possible
(Note 1)
Possible
(Note 1)
Possible
(Note 1)
Possible
(Note 1)
Possible
(Note 3)
Possible
Possible
(Note 1)
Possible
(Note 2)
Possible
(Note 1)
Possible
(Note 4)
Possible
(Note 4)
Table 1.17.1. Comparison of functions of UART0 through UART2