M37221 Mitsubishi, M37221 Datasheet - Page 17

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

SERIAL I/O
The M37221EF-XXXSP has a built-in serial I/O which can either trans-
mit or receive 8-bit data in serial in the clock synchronous mode.
The serial I/O block diagram is shown in Figure 10. The synchroniz-
ing clock I/O pin (S
as port P2.
Bit 2 of the serial I/O mode register (address 00DC
the synchronizing clock is supplied internally or externally (from the
P2
whether f(X
port P2 is used for serial I/O or not. To use the P2
pin, set the bit 2 of the port P2 direction register (address 00C5
“0.”
The operation of the serial I/O function is described below. The func-
tion of the serial I/O differs depending on the clock source; external
clock or internal clock.
Fig. 10. Serial I/O block diagram
0
/S
CLK
P2
P2
Note: When the data is set in the serial I/O register (address 00DD
pin). When an internal clock is selected, bits 1 and 0 select
P2
1
0
/S
IN
/S
2
/S
) is divided by 4, 16, 32, or 64. Bit 3 selects whether
OUT
X
CLK
IN
IN
CLK
), and data I/O pins (S
P2
P2
SM3
SM3
1
0
1/2
latch
latch
Synchronization circuit
1/2
SM6
OUT
SM5: LSB
, S
2
16
/S
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
) selects whether
IN
IN
) also function
pin as the S
Serial I/O shift register (8)
16
) to
SM2
Serial I/O counter (8)
MSB
S
IN
M37221EF-XXXSP,M37221EFSP
(Address 00DD
(Note)
16
), the register functions as the serial I/O shift register.
Frequency
divider
1/4
1/8
8
16
with ON-SCREEN DISPLAY CONTROLLER
1/16
)
SM1
SM0
Data bus
SM : Serial I/O mode register
Serial I/O interrupt
request
Selection gate :
Connected to black
colored side at reset.
17