UPD17708 datasheet(248/356 Pages) NEC

248 / 356 page

248

µPD17704, 17705, 17707, 17708, 17709

16.3.4 Presettable shift register 1

Presettable shift register 1 is an 8-bit shift register that writes serial out data and reads serial in data.

This register writes or reads data via data buffer.

It outputs the contents of the most significant bit (MSB) from the serial data I/O pin in synchronization with the falling

edge of the shift clock (during transmission operation), and reads data to the least significant bit (LSB) in synchronization

with the rising edge of the serial clock.

Figure 16-18 shows the configuration of the presettable shift register 1.

Figure 16-18. Configuration of Presettable Shift Register 1

Note

Data may be destroyed if the PUT or GET instruction is executed during serial communication. For details,

refer to 16.3.7 Cautions on setting and reading data.

16.3.5 Wait control block

The wait control block keeps communication waiting or releases communication from the wait status.

Serial communication is started when communication is released from the wait status by using the SIO1TS flag

of the serial I/O1 mode selection register.

Communication is set in the wait status eight clocks after the wait status has been released and communication

has been started.

The communication status can be detected by using the SIO1TS flag. To do so, detect the status of the SIO1TS

flag after setting this flag to “1”.

If “0” is written to the SIO1TS flag when communication is released from the wait status, the wait status is set. This

wait status is called forced wait status.

For the configuration of the serial I/O1 mode selection register, refer to Figure 16-17.

Data buffer

DBF3

Don't care

DBF2

Don't care

Name

Presettable

shift register 1

Symbol

SIO1SFR

Peripheral

04H

DBF1

DBF0

b3 b2

b1 b0

b5 b4

Peripheral register

D3 D2 D1 D0

D7 D6 D5 D4

← D6 ← D5 ← D4 ← D3 ← D2 ← D1 ← D0

Serial out

Serial in

Transfer data

Valid data

Sets serial out data and reads serial in data

GETNote

PUTNote

UPD17708 Datasheet(PDF) 248 Page - NEC

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