M37225M6_15 Datasheet, PDF (29/128 Pages) Renesas Technology Corp – SNGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER with ON-SCREEN DISPLAY CONTROLLER

M37225M6/M8/MA/MC-XXXSP, M37225ECSP
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 P2.
Bit 3 of the serial I/O mode register (address 00DC16) 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 4, 16, 32, or 64. To use SIN pin
for serial I/O, set the corresponding bit of the port P2 direction regis-
ter (address 00C516) to “0.”
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.
XIN
SCLK
SOUT
SIN
Data bus
1/2
1/2
Synchronous
circuit
SM2
S
Frequency divider
1/4 1/16 1/32 1/64
SM1
SM0
P20 latch
SM3
P21 latch
SM3
Serial I/O counter (8)
SM6
SM5 : LSB
MSB
(See note)
Serial I/O shift register (8)
8 ^{(Address 00DD16)}
Selection gate : Connected to
black side at
reset
SM : Serial I/O mode register
Serial I/O
interrupt request
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. 8.5.1 Serial I/O Block Diagram
Rev.1.00 Nov 01, 2000 page 27 of 124
REJ03B0136-0100Z