M37221M6_03 Datasheet, PDF (16/62 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER with ON-SCREEN DISPLAY CONTROLLER

MITSUBISHI MICROCOMPUTERS
M37221M6-XXXSP
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
with ON-SCREEN DISPLAY CONTROLLER
SERIAL I/O
The M37221M6-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 8. The synchronizing
clock I/O pin (SCLK), and data I/O pins (SOUT, SIN) also function as
port P2.
Bit 2 of the serial I/O mode register (address 00DC16) selects whether
the synchronizing clock is supplied internally or externally (from the
P20/SCLK pin). When an internal clock is selected, bits 1 and 0 select
whether f(XIN) is divided by 4, 16, 32, or 64. Bit 3 selects whether
port P2 is used for serial I/O or not. To use the P22/SIN pin as the SIN
pin, set the bit 2 of the port P2 direction register (address 00C516) to
“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.
XIN
P20/SCLK
P21/SOUT
P22/SIN
1/2
P20 latch
SM3
P21 latch
SM3
1/2
Synchronization circuit
SM2
S
Data bus
Frequency
divider
1/4 1/8 1/16
SM1
SM0
Selection gate :
Connected to black
colored side at reset.
SM : Serial I/O mode register
Serial I/O counter (8)
Serial I/O interrupt
request
SM5 : LSB
MSB
(Note)
Serial I/O shift register (8)
SM6
(Address 00DD16)
8
Note : When the data is set in the serial I/O register (address 00DD16), the register functions as the serial I/O shift register.
Fig. 8. Serial I/O block diagram
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