M38B53M4-059FP datasheet(49/355 Pages) MITSUBISHI

49 / 355 page

38B5 Group User’s Manual

1-33

HARDWARE

FUNCTIONAL DESCRIPTION

When the external synchronous clock is selected, input an “H” level

signal into the SBUSY1 input and an “L” level signal into the SBUSY1

input in the initial status in which transfer is stopped. At this time,

the transfer clocks to be input in SCLK1 become invalid.

During serial transfer, the transfer clocks to be input in SCLK1 be-

come valid, enabling a transmit/receive operation, while an “L” level

signal is input into the SBUSY1 input and an “H” level signal is input

into the SBUSY1 input.

When changing the input values in the SBUSY1 input and the SBUSY1

input at these operations, change them when the SCLK1 input is in a

high state.

When the high impedance of the SOUT1 output is selected by the

SOUT1 pin control bit (b6), the SOUT1 output becomes active, en-

abling serial transfer by inputting a transfer clock to SCLK1, while an

“L” level signal is input into the SBUSY1 input and an “H” level signal

is input into the SBUSY1 input.

3. SBUSY1 output signal

The SBUSY1 output is a signal which requests a stop of transmis-

sion/reception to the serial transfer destination. In the automatic

transfer serial I/O mode, regardless of the internal or external syn-

chronous clock, whether the SBUSY1 output is to be active at trans-

fer of each 1-byte data or during transfer of all data can be selected

by the SBUSY1 output • SSTB1 output function selection bit (b4).

In the initial status, the status in which the serial I/O initialization bit

(b4) is reset to “0,” the SBUSY1 output goes to “H” and the SBUSY1

output goes to “L.”

Fig. 27 SBUSY1 input operation (internal synchronous clock)

Fig. 28 SBUSY1 input operation (external synchronous clock)

(4) Handshake Signal

1. SSTB1 output signal

The SSTB1 output is a signal to inform an end of transmission/re-

ception to the serial transfer destination . The SSTB1 output signal

can be used only when the internal synchronous clock is selected.

In the initial status, namely, in the status in which the serial I/O

initialization bit (b4) is reset to “0,” the SSTB1 output goes to “L,” or

the SSTB1 output goes to “H.”

At the end of transmit/receive operation, when the data of the serial

I/O1 register is all output from SOUT1, pulses are output in the pe-

riod of 1 cycle of the transfer clock so as to cause the SSTB1 output

to go “H” or the SSTB1 output to go “L.” After that, each pulse is

returned to the initial status in which SSTB1 output goes to “L” or the

SSTB1 output goes to “H.”

Furthermore, after 1 cycle, the serial transfer status flag (b5) is re-

set to “0.”

In the automatic transfer serial I/O mode, whether the SSTB1 output

is to be active at an end of each 1-byte data or after completion of

transfer of all data can be selected by the SBUSY1 output • SSTB1

output function selection bit (b4 of address 001A16) of serial I/O1

control register 2.

2. SBUSY1 input signal

The SBUSY1 input is a signal which receives a request for a stop of

transmission/reception from the serial transfer destination.

When the internal synchronous clock is selected, input an “H” level

signal into the SBUSY1 input and an “L” level signal into the SBUSY1

input in the initial status in which transfer is stopped.

When starting a transmit/receive operation, input an “L” level signal

into the SBUSY1 input and an “H” level signal into the SBUSY1 input in

the period of 1.5 cycles or more of the transfer clock. Then, transfer

clocks are output from the SCLK1 output.

When an “H” level signal is input into the SBUSY1 input and an “L”

level signal into the SBUSY1 input after a transmit/receive operation

is started, this transmit/receive operation are not stopped immedi-

ately and the transfer clocks from the SCLK1 output is not stopped

until the specified number of bits are transmitted and received.

The handshake unit of the 8-bit serial I/O is 8 bits and that of the

automatic transfer serial I/O is 8 bits.

Fig. 26 SSTB1 output operation

SSTB1

SCLK1

SOUT1

Serial transfer

status flag

SBUSY1

SCLK1

SOUT1

SBUSY1

SCLK1

SOUT1

Invalid

(Output high-impedance)

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