deveopmen
Clock synchronous serial I/O mode
Rev.B2 for proof reading
Mitsubishi Microcomputers
M32C/83 group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
177
(1) Clock synchronous serial I/O mode
The clock synchronous serial I/O mode uses a transfer clock to transmit and receive data. Tables 1.18.1
and 1.18.2 list the specifications of the clock synchronous serial I/O mode.
Table 1.18.1. Specifications of clock synchronous serial I/O mode (1/2)
Item
Transfer data format
Transfer data length: 8 bits
Transfer clock
When internal clock is selected (bit 3 at addresses 0368
16
, 02E8
16
, 0338
16
, 0328
16
,
02F8
16
=
“
0
”
) : fi/ 2(m+1)
(Note 1)
fi = f
1
, f
8
, f
2n
(Note 2)
_
CLK is selected by the corresponding peripheral function select register A, B and C.
When external clock is selected (bit 3 at addresses 0368
16
, 02E8
16
, 0338
16
, 0328
16
,
02F8
16
=
“
1
”
) : Input from CLKi pin
_
Set the corresponding function select register A to I/O port
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 036D
16
, 02ED
16
, 033D
16
, 032D
16
, 02FD
16
) =
“
1
”
_
Transmit buffer empty flag (bit 1 at addresses 036D
16
, 02ED
16
, 033D
16
, 032D
16
, 02FD
16
) =
“
0
”
_
When CTS function selected, CTS input level =
“
L
”
_
TxD output is selected by the corresponding peripheral function select register A, B and C.
Furthermore, if external clock is selected, the following requirements must also be met:
_
CLKi polarity select bit (bit 6 at addresses 036C
16
, 02EC
16
, 033C
16
, 032C
16
,
02FC
16
) =
“
0
”
: CLKi input level =
“
H
”
_
CLKi polarity select bit (bit 6 at addresses 036C
16
, 02EC
16
, 033C
16
, 032C
16
,
02FC
16
) =
“
1
”
: CLKi input level =
“
L
”
Reception start condition
To start reception, the following requirements must be met:
_
Receive enable bit (bit 2 at addresses 036D
16
, 02ED
16
, 033D
16
, 032D
16
, 02FD
16
) =
“
1
”
_
Transmit enable bit (bit 0 at addresses 036D
16
, 02ED
16
, 033D
16
, 032D
16
, 02FD
16
) =
“
1
”
_
Transmit buffer empty flag (bit 1 at addresses 036D
16
, 02ED
16
, 033D
16
, 032D
16
, 02FD
16
) =
“
0
”
Furthermore, if external clock is selected, the following requirements must also be met:
_
CLKi polarity select bit (bit 6 at addresses 036C
16
, 02EC
16
, 033C
16
, 032C
16
,
02FC
16
) =
“
0
”
: CLKi input level =
“
H
”
_
CLKi polarity select bit (bit 6 at addresses 036C
16
, 02EC
16
, 033C
16
, 032C
16
,
02FC
16
) =
“
1
”
: CLKi input level =
“
L
”
When transmitting
_
Transmit interrupt cause select bit (bit 4 at address 036D
16
, 02ED
16
, 033D
16
,
032D
16
, 02FD
16
) =
“
0
”
: Interrupts requested when data transfer from UARTi trans-
fer buffer register to UARTi transmit register is completed
_
Transmit interrupt cause select bit (bit 4 at address 036D
16
, 02ED
16
, 033D
16
,
032D
16
, 02FD
16
) =
“
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
Specification
Transmission/reception control
Interrupt request
generation timing
Note 1:
“
m
”
denotes the value 00
16
to FF
16
that is set to the UART bit rate generator.