UPD78C18 datasheet(41/110 Pages) NEC

41 / 110 page

µPD78C17,78C18

2.8

SERIAL INTERFACE

The

µPD78C17 and 78C18 have the serial interface using the transmit/receive method by start/stop bit. The

three types of operating modes are shown below.

• Asynchronous (start-stop) mode : Establishes data bit synchronization and character synchronization

by start bit.

• Synchronous mode

: Data transfer is performed in synchronization with the serial clock.

• I/O interface mode

: As for serial data transfer in the

µPD7801/78C06A etc., data transfer

is performed in synchronization with the serial clock.

The serial interface block is composed of the serial data input (RxD), serial data output (TxD), 3 serial clock

input/output (SCK) pins, transfer control block, two 8-bit serial registers for transmission and reception, and 8-

bit transmission buffer and reception buffer (see Fig. 2-23).

As the serial registers and buffers for transmission and reception are provided, transmission or reception is

individually performed (full-duplex double buffer transmitter/receiver).

However, the serial clock (SCK) is shared in transmission and reception, and half-duplex transmission/

reception is performed in the synchronous mode and I/O mode.

Fig. 2-23 Serial Interface Block Diagram

Remarks

φ24 = fXX x 1/24

Where, fXX = oscillation frequency (MHz)

φ384 = fXX x 1/384

Internal Bus

INTSR

Receive Buffer (RXB)

Serial Mode Register

(SML, SMH)

Transmit Buffer (TXB)

Serial Register (S¡P)

Serial Register (P¡S)

PC1/R

×D

PC2/SCK

SK1, SK2

φ24

φ384

TO Output

PC0/T

×D

Control

Reception

Transmission

Control

INTST

UPD78C18 Datasheet(PDF) 41 Page - NEC

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