M37221 Mitsubishi, M37221 Datasheet - Page 18

• Manufacturer Part Number: M37221
• Description: SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER with ON-SCREEN DISPLAY CONTROLLER
• Manufacturer: Mitsubishi

Internal clock—the serial I/O counter is set to “7” during write cycle
into the serial I/O register (address 00DD
“H” forcibly. At each falling edge of the transfer clock after the write
cycle, serial data is output from the S
be selected by bit 5 of the serial I/O mode register. At each rising
edge of the transfer clock, data is input from the S
the serial I/O register is shifted 1 bit.
After the transfer clock has counted 8 times, the serial I/O counter
becomes “0” and the transfer clock stops at “H.” At this time the inter-
rupt request bit is set to “1.”
External clock—when an external clock is selected as the clock
source, the interrupt request is set to “1” after the transfer clock has
counted 8 times. However, transfer operation does not stop, so con-
trol the clock externally. Use the external clock of 1MHz or less with
a duty cycle of 50%.
The serial I/O timing is shown in Figure 12. When using an external
clock for transfer, the external clock must be held at “H” for initializing
the serial I/O counter. When switching between an internal clock and
an external clock, do not switch during transfer. Also, be sure to ini-
tialize the serial I/O counter after switching.
Notes 1: On programming, note that the serial I/O counter is set by
Fig. 12. Serial I/O timing (for LSB first)
18
Transfer clock
Synchroninzing clock
Serial I/O register
write signal
Serial I/O output
Serial I/O input
2: When an external clock is used as the synchronizing clock,
Note : When an internal clock is selected, the S
writing to the serial I/O register with the bit managing in-
structions as SEB and CLB instructions.
write transmit data to the serial I/O register at “H” of the
transfer clock input level.
S
S
OUT
IN
OUT
16
pin. Transfer direction can
), and transfer clock goes
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
IN
pin and data in
OUT
pin is at high-impedance after transfer is completed.
D
0
D
1
M37221EF-XXXSP,M37221EFSP
Fig. 11. Structure of serial I/O mode register
D
2
7
D
3
0
with ON-SCREEN DISPLAY CONTROLLER
D
4
MITSUBISHI MICROCOMPUTERS
D
0
5
Interrupt request bit is set to “1”
Serial input pin selection bit
Transfer direction selection bit
Serial I/O mode register
(SM : address 00DC
Internal synchronizing clock
selection bits
b1 b0
Synchronizing clock selection bit
Serial I/O port selection bit
Fix this bit to “0.”
0
0
1
1
0 : Input signal from S
1 : Input signal from S
0 : External clock
1 : Internal clock
0 : P2
1 : S
0 : LSB first
1 : MSB first
D
0 : f(X
1 : f(X
0 : f(X
1 : f(X
6
CLK
0
, P2
IN
IN
IN
IN
, S
)/4
)/16
)/32
)/64
D
OUT
1
7
functions as port
(Note)
16
)
IN
OUT
pin
pin