FS98O21 datasheet(71/136 Pages) FORTUNE

71 / 136 page

FS98O21

Rev. 1.7

71/136

Digital I/O Port or I2C Serial Port : PT2[3]/SDA, PT2[4]/SCL

PT2PU[4:3]

PT2EN[4:3]

PT2[4:3]

LOAD

Write

AR==PT2

READ&AR==PT2

Databus[7:0]

PT2OC[4:3]

Open Drain Control

Figure 7-4 PT2[3] PT2[4] function block

GPIO Port 2 Bit4 and Bit 3 (PT2[4:3]) function block is shown in Figure 7-4. The main function of the GPIO is

input and output data between the Data bus and the ports. Users could control the PT2EN[4:3] register flags to

decide the input output direction. The input and output function and the related functions are explained as

follows:

Input:

GPIO Port 2 Bit4 and Bit3 (PT2[4:3]) could be the I2C Module SCL and SDA ports or be the general I/O

ports. User should setup I2CEN register flag to decide the I2C Module is enabled or not. The detailed I2C

Module usage is described in Chapter 9.

The input port has a Schmitt trigger in it, and the up/down trigger voltage level is 0.45VDD/0.2VDD.

Output

FS98O21 sends the digital data out by an embedded D Flip Flop. When the program sends data out

through PT2, the data will be sent to data bus first, and then the D Flip Flop will latch the signal for PT2

output while the Write signal and AR (FS98O21 internal device address pointer) is pointed to PT2.

Pull up resistor

FS98O21 embeds an internal pull up resistor function in PT2 with about 1000k ohm resistor

15. User could

control the PT2PU[4:3] register flags to decide the connections to pull up resistor. When a port is

connected to the pull up resistor, the input data is, by default, assigned to high (data 1).

Open Drain Control

FS98O21 embeds an internal Open Drain Control function in PT2[4:3]. Users could control the

PT2OC[4:3] register flags to decide if the Open Drain Control function is enabled. When the user assigns

these 2 ports to be SCL and SDA, PT2OC[4:3] should be set. Please refer to Chapter 9.

15 The pull up current is about 10uA. Remember to disable PT1PU before program falls into Sleep mode.

FS98O21 Datasheet(PDF) 71 Page - Fortune Semiconductor Corp.