M37630M4T Datasheet, PDF (25/48 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
7630 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
SERIAL I/Os
The serial I/O section of 7630 group consists of one clock synchro-
nous and one asynchronous (UART) interface.
Clock Synchronous Serial I/O (SI/O)
The clock synchronous interface allows full duplex communication
based on 8 bit word length. The transfer clock can be selected from
an internal or external clock. When an internal clock is selected, a
programmable clock divider allows eight different transmission
speeds. Refer to Block diagram of clock synchronous I/O (f is inter-
nal system clock). The operation of the clock synchronous serial I/O
can be configured by the serial I/O control register SIOCON; refer to
Fig. 25.
φ
SIOCON_{2, 1, 0}
Clock divider
P2₃/S_RDY
P2₂/S_CLK
P2₁/S_OUT
P2₀/S_IN
SIOCON₄
“1”
“0”
P2₃ latch
SIOCON₃
“1”
“0”
P2₂ latch
SIOCON₃
“1”
“0”
P2₁ latch
SIOCON₃
“1”
“0”
P2₀ latch
Sync. circuit
SIO counter (3)
SIO shift register (8)
SIOCON₆
“1”
“0”
SIO interrupt
Fig. 23 Block diagram of clock synchronous I/O (φ is internal system clock)
(1) Clock synchronous serial I/O operation
Either an internal or external transfer clock can be selected by bit 6
of SIOCON. The internal clock divider can be programmed by bits 0
to 2 of SIOCON. Bit 3 of SIOCON determines whether the double
function pins P2₀ to P2₂ will act as I/O ports or serve as SIO pins.
Bit 4 of SIOCON allows the same selection for pin P2₃.
When an internal transfer clock is selected, transmission can be
triggered by writing data to the SI/O shift register (SIO, address
0012₁₆). After an 8–bit transmission has been completed, the S_OUT
pin will change to high impedance and the SIO interrupt request bit
will be set to “1”.
When an external transfer clock is selected, the SIO interrupt
request bit will be set to “1” after 8 cycles but the contents of the
SI/O shift register continue to be shifted while the transfer clock is
being input. Therefore, the clock needs to be controlled externally;
the S_OUT pin will not change to high impedance automatically.
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