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SL811HS and SL811HST: Application Notes

and specifications contained in this document are subject to change without

notice.

Date: 07/26/01

Revision: 1.21

Page: 19

3.4. Interrupt Status Register

The ISR is a Read/Write register providing interrupt status. Writing to this register can

clear interrupts. To clear a specific interrupt, the register is written with corresponding

bit set to “1”.

NOTE1:

This bit is shared between USB_RESET and Resume interrupt detection. When bit-6 of

bit is used to indicate detection of USB RESET.

NOTE2:

Bit-5 is provided to support USB cable Insertion/Removal detection for the SL811HS in

Host Mode. This bit is set whenever a cable is inserted or removed from the USB port. It

should be cleared after a removal or insertion is detected so that the next event can be

detected.

Bit 6 is updated whenever a USB reset is detected, or when in suspend state the detection

of a ‘K’ or SE0 state

• Bit 7 provides continuous USB Data+ line status. Bit 7 in conjunction with bit 6 and 5 can

be used to detect if a Low or Full speed device is connected after USB reset is issued. The

bit should be read immediately after a USB reset and before USB activity begins for a valid

state.

• On Power up, before generating a USB Reset, the state of the USB Reset bit will be = ‘1’ if

no device is connected, i.e. a ‘SE0’ on the USB. If the bit is ‘0’ then it indicates a device is

attached. If the D+ (bit 7) is a ‘1’ then the attached device is a Full Speed device, if D+ is a

‘0’ then it is a Low Speed Device.

• After a USB Reset has been generated and the USB is idle, the same procedure can be

used to determine if a device is attached. The SL811HS is continually monitoring the USB

and if a ‘SE0” state continuously exists on the USB the USB reset bit will be ‘1’ indicating

no device attached. If ‘0’ then device attached and speed can be determined by viewing

the state of bit 7.

Bit Position Bit Name Function

0 USB-A USB-A done Interrupt.

1 USB-B USB-B done Interrupt.

2 Babble Detection 1=enable interrupt on babble detection

3 Reserved

4 SOF timer 1=enable interrupt on 1ms SOF timer

5 Insert/Remove Slave Insert/Remove detection (Note 2)

6 USB Reset/Resume Enable USB Reset/Resume Interrupt. (note 1)

7 D+ Value of the Data+ pin

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 42 43

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