NEC uPD78054(A) Manuale Utente

The 3-wire serial I/O mode is valid for connection of peripheral I/O units and display controllers which incorporate

a conventional synchronous serial interface such as the 75X/XL, 78K and 17K series.

Communication is carried out with three lines of serial clock (SCK1), serial output (SO1) and serial input (SI1).

The 3-wire serial I/O 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.

If the external clock input has been selected with CSIM11 set to 0, set bit 1 (BUSY1) and bit 2 (STRB)

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

×

:  Don't care

Notes 1. Can be used freely as port function.

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

to 0).

×

:  Don't care

PM

××

:  Port mode register

P

××

:  Port output latch

6

<5>

4

3

2

1

0

<7>

Symbol

CSIM1 CSIE1

DIR

ATE

0

0

0

CSIM11 CSIM10

CSIM11

0

1

Serial Interface Channel 1 Clock Selection

Clock externally input to SCK1 pin

8-bit timer register 2 (TM2) output

1

Clock specified with bits 4 to 7 of timer clock select register 3 (TCL3)

CSIM10

×

0

1

FF68H              00H          R/W

Address     After Reset     R/W

ATE

0

1

Serial Interface Channel 1 Operating Mode Selection

3-wire serial I/O mode

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

DIR

0

1

Start Bit

MSB

LSB

SO1 Pin Function

SI1/P20

(Input)

SO1 Pin Function

SO1

(CMOS output)

Operation

enable

SCK1

(Input)

CSIE1

0

CSIM11

P20 PM21 P21 PM22

Shift Register 1

Operation

Serial Clock Counter

Operation Control

SI1/P20 Pin

Function

SCK1/P22

Pin Function

×

1

0

1

0

×

0

0

1

×

1

Count

operation

SI1

(Input)

×

×

×

×

×

Operation

stop

Clear

P20 (CMOS

input/output)

P22 (CMOS

input/output)

×

PM20

SO1/P21 Pin

Function

SO1 (CMOS

output)

P21 (CMOS

input/output)

SCK1

(CMOS

output)

1

P22