FS98O21 datasheet(69/136 Pages) FORTUNE

69 / 136 page

FS98O21

Rev. 1.7

69/136

Digital I/O Port or PDM Output : PT2[2]

PT2PU[2]

PT2EN[2]

PT2[2]

LOAD

Write

AR==PT2

READ&AR==PT2

Databus[7:0]

Figure 7-3 PT2[2] function block

GPIO Port 2 Bit2 (PT2[2]) function block is shown in Figure 7-3. The main function of the GPIO is input and

output data between the Data bus and the ports. User could control the PT2EN[2] 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 Bit2 (PT1[2]) could be the PDM (Pulse Density Modulator) output port or be the general I/O

port. User should setup PM1EN register flag to decide if the PDM is enabled. The detailed PDM usage is

described in Chapter 8.

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

13. Users

could control the PT2PU[2] register flags to decide the connection 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).

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

FS98O21 Datasheet(PDF) 69 Page - Fortune Semiconductor Corp.