SPCA514A 查看數據表（PDF） - Unspecified

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SPCA514A

Digital Audio USB Controller

Unspecified 

SPCA514A

  



 


 

 

  

 

From normal to suspend state:

To enter suspend state, the firmware must program register 0X8002 bit 0. The

SPCA514 will stop the crystal oscillation if this bit is set.

From the application’s point of view, there are two possible causes to put the chip into

suspend state. The first one is the USB suspend. After the USB bus is idle for 6 ms, the

SPCA514 will issue an interrupt to inform the micro-controller. Then the micro-controller

must program the bit 0 of register 0X8002.

The other cause to enter suspend state is that when the UI is idle longer than a period

of time. This part is completely implemented by the firmware. The SPCA514 hardware has

no interrupt for this. Like the USB suspend, if the firmware decide the UI idle time is long

enough, it must program bit 0 of register 0X8002 to put the chip into suspend state.

From suspend to normal state

As stated above, before the SPCA514 returns to normal state from suspend state, it

must goes through the resume state. There are two possible causes for the SPCA514 to

enter resume state from suspend state.

(1) When bit 4 of register 0X8003 is set and the USB controller detects a bus activity on

the USB bus.

(2) When bit 5 of register 0X8003 is set and the SPCA514 detects a key status change via

GPIO pins.

All the two causes are processed by SPCA514 automatically, no firmware intervention

needed. Since the clock is stopped during suspend, it’s not possible for the micro-

controller to do anything about it. The length of internal resume period can be

programmed from 1 ms to 20 ms via bit[3:0] of register 0X8003.

 

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