W55P241

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4. BLOCK DIAGRAM

Figure 1 W55P241 Block Diagram

5. FUNCTIONAL DESCRIPTION

The W55P241 provides up to three bi-directional ports. Each bi-directional port has 8 pins (BP00~07,

BP10~17, or BP20~27) and each bi-directional pin can be configured as an output pin or input pin

independently. One dedicated wakeup pin forcibly releases the microcontroller from the standby mode.

When selected as an input pin, the state change on each pin can trigger interrupt request, if the

corresponding interrupt enabling bit is set. These three bi-directional ports, when programmed as an

output port, can sink at least 25-mA current in order to drive LED directly. With an embedded 256-level

output circuit, motor speed control and LED brightness are available in BP00~BP07.

5.1 SPI

SPI is a direct and simple interface that uses 4 pads (/CS, CLK, DI and DO) for data exchange

between master and slave. W55P241 operates in the slave mode and up to 2 W55P241 devices can

function simultaneously. The master identifies the slaves which are differentiated by the DIS pad.

Because W55P241 operates in mode 0 only, the CLK idle state is always

“0”, “receive data” is always

latched at the rising edge of CLK, and

“transmit data” is always changed (if at all) at the falling edge of

CLK. To control one SFR of W55P241, 16 bits of serial data must be transmitted from the master. 16

bits of serial data consist of 1 command byte and 1 data byte. Basically, 4 groups of commands are

defined and the IO port group suffices to generate all possible IO statuses. Users may use 3 other

speedup groups to minimize microcontroller load.

SPI

Control

Logic

/CS

CLK

DI

DO

PORTA

(PWM)

PORTB

PORTC

8

8

8

I/O

BP00-BP07

DIS

WAKEUP

Timing

Generator

Read

Write

Control

Buffer

8-bit

Internal

Data Bus

I/O

BP10-BP17

I/O

BP20-BP27

BP0

(PWM)

BP1

BP2