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SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
and ON-SCREEN DISPLAY CONTROLLER
M37272M6/M8–XXXSP/FP, M37272MA–XXXSP
M37272E8SP/FP, M37272EFSP
MITSUBISHI MICROCOMPUTERS
Rev. 1.3
8
Serial I/O shift register (8)
Data bus
Serial I/O
interrupt request
Selection gate: Connect to
black side at
reset.
Synchronous
circuit
Frequency divider
1/81/4 1/16
SM1
SM0
Serial I/O counter (8)
SM5
: LSB
MSB
S
SM2
1/2
X
IN
S
IN
S
OUT
S
CLK
1/2
X
CIN
1/2
CM7
1/2
Note : When the data is set in the serial I/O register (address 00EA
(See note)
CM : CPU mode register
SM : Serial I/O mode register
16
), the register functions as the serial I/O shift register.
P2
0
Latch
SM3
P2
1
Latch
SM3
SM6
8.5 SERIAL I/O
This microcomputer has a built-in serial I/O which can either transmit
or receive 8-bit data serially in the clock synchronous mode.
The serial I/O block diagram is shown in Figure 8.5.1. The synchro-
nous clock I/O pin (SCLK), and data output pin (SOUT) also function
as port P4, data input pin (SIN) also functions as port P20–P22.
Bit 3 of the serial I/O mode register (address 00EB16) selects whether
the synchronous clock is supplied internally or externally (from the
SCLK pin). When an internal clock is selected, bits 1 and 0 select
whether f(XIN) or f(XCIN) is divided by 8, 16, 32, or 64. To use the SIN
pin for serial I/O, set the corresponding bit of the port P2 direction
register (address 00C516) to “0.”
Fig. 8.5.1 Serial I/O Block Diagram
The operation of the serial I/O is described below. The operation of
the serial I/O differs depending on the clock source; external clock or
internal clock.
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