NEC PD78078 用户手册

The following three operating modes are available to the serial interface channel 1.

•

Operation stop mode

•

3-wire serial I/O mode

•

3-wire serial I/O mode with automatic transmit/receive function

Serial transfer is not carried out in the operation stop mode.  Thus, power consumption can be reduced.  The

serial I/O shift register 1 (SIO1) does not carry out shift operation either, and thus it can be used as an ordinary

8-bit register.

In the operation stop mode, the P20/SI1, P21/SO1, P22/SCK1, P23/STB, and P24/BUSY pins can be used as

ordinary input/output ports.

The operation stop mode is set with the serial operating mode register 1 (CSIM1).

CSIM1 is set with a 1-bit or 8-bit memory manipulation instruction.

RESET input sets CSIM1 to 00H.

Notes 1. Can be used freely as port function.

2. Can be used as P20 (CMOS input/output) when only transmitter is used (set bit 7 (RE) of the

automatic data transmit/receive control register (ADTC) to 0).

x

:  Don’t care

PMxx :  Port mode register

Pxx

:  Port output latch

Operation

enable

6

<5>

4

3

2

1

0

<7>

Symbol

CSIM1 CSIE1

DIR

ATE

0

0

0

CSIM11 CSIM10

SCK1

(Input)

CSIE

1

0

FF68H              00H          R/W

Address     After Reset     R/W

CSIM

11

P20 PM21 P21 PM22

Shift Register

1 Operation

Serial Clock Counter

Operation Control

SI1/P20 Pin

Function

SCK1/P22

Pin Function

x

1

0

1

0

x

0

0

1

x

1

Count

operation

SI1

(Input)

x

x

x

x

x

Operation

stop

Clear

P20 (CMOS

input/output)

P22 (CMOS

input/output)

x

PM20

SO1/P21 Pin

Function

SO1 (CMOS

output)

P21 (CMOS

input/output)

SCK1

(CMOS
output)

1

P22