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FSA9280A

USB Port Multimedia Switch Featuring Automatic Select and Accessory Detection

Fairchild Semiconductor 

4. Configuration

FSA9280A requires minimal configuration for proper

detection and reporting. The following steps can be followed

for full configuration. In many cases, only Step 5 needs to be

implemented for proper operation.

1. Write Control register (02h) to configure different

switching configurations and wait timing.

2. Write Interrupt Mask 1 and 2 registers (05h, 06h) to

mask any interrupts not required in the application.

5. Detection

The FSA9280A detection algorithms monitor both the VBUS

and ID pins of the USB interface. Based on the detection

results, multiple registers are updated and the INTB pin is

asserted to indicate to the baseband processor that an

accessory was detected and to read the registers for the

complete information.

FSA9280A Standby

Mode

3. Write Timing Set 1 (08h) register to program required

key-press timing and ADC-detection timing.

4. Write Timing Set 2 (09h) register to program required

Switching Wait timing and Long Key Press timing.

5. Write Control register (02h) to clear INT Mask bit. This

enables interrupts to the baseband.

The detection algorithm allows the application to control the

timing of the detection algorithm and the configuration of the

internal switches. The flow diagram in Figure 7 shows the

operation of the detection algorithm.

Accessory Plug-in

FSA9280A Detects

Accessory Type

FSA9280A Writes Device

Type registers and Attach

Interrupt

Set INTB Pin LOW (INT

MASK bit must have been

cleared by µP)

NO

µP reads FSA9280A

Interrupt Registers

VDDIO

=0V ?

YES

FSA9280A waits

Switching Wait time

Is

Accessory

detected a

USB or

Factory

NO

Mode

YES

FSA9280A auto-

conf igures switch

paths

FSA9280A Writes Device

Type registers and Attach

Interrupt

FSA9280A set INTB Pin

LOW (INT MASK bit must

have been cleared by µP)

µP reads FSA9280A

Interrupt Registers

FSA9280A takes no

action until Wait bit is

set HIGH by

processor

NO Wait

Bit = 1

?

YES

NO

Detach

?

YES

FSA9280A writes

Detach Interrupt

YES

FSA9280A auto-

conf igures switch

paths

Manual

Switch =

1?

FSA9280A sets INTB

Pin LOW (INT MASK

NO

bit must have been

cleared by µP)

FSA9280A conf igures

switches according to

Manual SW 1 /2

registers

© 2009 Fairchild Semiconductor Corporation

FSA9280A • Rev 1.1.0

Detach

?

NO

YES

FSA9280A writes

Detach Interrupt and

clears Device Type

register

Figure 7. Detection Flow Chart

FSA9280A set s

INTB Pin LOW (INT

MASK bit must have

been cleared by µP)

8

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