Serial I/O (Special Modes)
172
Mitsubishi microcomputers
M16C / 62P Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
development
Preliminary Specifications Rev.1.0
Specifications in this manual are tentative and subject to change.
Special Mode 2
Multiple slaves can be serially communicated from one master. Synchronous clock polarity and phase
are selectable. Table 1.20.6 lists the specifications of Special Mode 2. Table 1.20.7 lists the registers
used in Special Mode 2 and the register values set. Figure 1.20.5 shows communication control example
for Special Mode 2.
Table 1.20.6. Special Mode 2 Specifications
Item
Transfer data format
Transfer clock
Specification
Transfer data length: 8 bits
Master mode
UiMR(i=0 to 2) register’s CKDIR bit = “0” (internal clock) : fj/ 2(n+1)
fj = f
1SIO
, f
2SIO
, f
8SIO
, f
32SIO
. n: Setting value of UiBRG register 00
16
to FF
16
Slave mode
CKDIR bit = “1” (external clock selected) : Input from CLKi pin
Controlled by input/output ports
Before transmission can start, the following requirements must be met (Note 1)
_
The TE bit of UiC1 register= 1 (transmission enabled)
_
The TI bit of UiC1 register = 0 (data present in UiTB register)
Before reception can start, the following requirements must be met (Note 1)
_
The RE bit of UiC1 register= 1 (reception enabled)
_
The TE bit of UiC1 register= 1 (transmission enabled)
_
The TI bit of UiC1 register= 0 (data present in the UiTB register)
For transmission, one of the following conditions can be selected
_
The UiIRS bit of UiC1 register = 0 (transmit buffer empty): when transferring data
from the UiTB register to the UARTi transmit register (at start of transmission)
_
The UiIRS bit =1 (transfer completed): when the serial I/O finished sending data from
the UARTi transmit register
For reception
When transferring data from the UARTi receive register to the UiRB register (at
completion of reception)
Overrun error (Note 2)
This error occurs if the serial I/O started receiving the next data before reading the
UiRB register and received the 7th bit of the next data
Clock phase setting
Selectable from four combinations of transfer clock polarities and phases
Note 1: When an external clock is selected, the conditions must be met while if the UiC0 register’s CKPOL bit = “0”
(transmit data output at the falling edge and the receive data taken in at the rising edge of the transfer clock),
the external clock is in the high state; if the UiC0 register’s CKPOL bit = “1” (transmit data output at the rising
edge and the receive data taken in at the falling edge of the transfer clock), the external clock is in the low
state.
Note 2: If an overrun error occurs, the value of UiRB register will be indeterminate. The IR bit of SiRIC register does
not change.
Transmit/receive control
Transmission start condition
Reception start condition
Error detection
Select function
Interrupt request
generation timing