29
3819 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
(2.3) When Selecting the Internal Clock
When selecting the internal clock, the P67/SRDY1/CS/SCLK12 pin
can be used as the SRDY1 pin by setting SC14 to “1”.
When selecting the internal clock, the P67 pin can be used as the
synchronous clock output pin SCLK12 by setting SIOAC3 to “1”. In
this case, the SCLK11 pin goes to high impedance state.
Select the function of the P67/SRDY1/CS/SCLK12 and P66/SCLK11
with the following registers (refer to Table 2):
qthe bit 3 (SC13), the bit 4(SC14), and the bit 6(SC16) of the se-
rial I/O1 control register
qthe bit 3 (SIOAC3) of the serial I/O automatic transfer control
register
When using both the SCLK11 and SCKL12 by switching, switch the
P67/SRDY1/CS/SCLK12 to the P67 (SC14=0) and set the P67 direc-
tion register to input mode. Note that switch SIOAC3 during “H” of
transfer clock at the completion of automatic transfer.
Table 2. SCLK11 and SCLK12 selection
SC16
1
SC14
0
SC33
1
SIOAC3
0
1
P66/SCLK11
SCLK11
High
impedance
P67/SCLK12
P67
SCLK12
Note : SC13: Serial I/O1 port selection bit
SC14: SRDY1 output selection bit
SC16: Synchronous clock selection bit
SIOAC3: Synchronous clock output pin selection bit
Fig. 20 Timing diagram during serial I/O automatic transfer (internal clock selected, SRDY used)
Fig. 21 Timing during serial I/O automatic transfer (internal clock selected, SCLK11 and SCLK12 used)
DI6
DI0
DO0
DO7
Bit 1 write signal of serial I/O
automatic transfer control
register
Serial I/O output
Sout
Serial I/O input
SIN
DI0
Transfer interval
Bit 1 of serial I/O automatic
transfer control register
Write signal from RAM to
serial I/O1 register
Write signal from serial I/O1
register to RAM
Transfer clock
Data pointer
(internal or SCLK output)
Receive
enabled signal
SRDY
n-1
0
n
DO1 DO2 DO3 DO4 DO5 DO6 DO7
DO6
DI1 DI2 DI3 DI4 DI5 DI6 DI7
DI7
DO0
DI7
Bit 1 write signal of serial I/O
automatic transfer control
register
Serial I/O output
Sout
Serial I/O input
SIN
Transfer interval
Bit 1 of serial I/O automatic
transfer control register
Write signal from RAM to
serial I/O1 register
Write signal from serial I/O1
register to RAM
Data pointer
m-1
0
m
DO0
Bit 3 of serial I/O automatic
transfer control register
Transfer clock
(internal)
SCLK11 output
SCLK12 output
n
DO1 DO2 DO3 DO4 DO5 DO6 DO7
DO0
DO6 DO7
DO0 DO1 DO2 DO3
DI0
DI1
DI2
DI3
DI4
DI5
DI6
DI7
DI0
DI1
DI2
DI3
DI6