Rainbow Electronics AT89C51SND1C - Manual (Page 100)

100
AT8xC51SND1C
4109E–8051–06/03
Table 91. USBADDR Register
USBADDR (S:C6h) – USB Address Register
Reset Value = 0000 0000b
Table 92. USBINT Register
USBINT (S:BDh) – USB Global Interrupt Register
Reset Value = 0000 0000b
7 6 5 4 3 2 1 0
FEN UADD6 UADD5 UADD4 UADD3 UADD2 UADD1 UADD0
Bit
Number
Bit
Mnemonic Description
7 FEN
Function Enable Bit
Set to enable the function. The device firmware should set this bit after it has
received a USB reset and participate in the following configuration process with
the default address (FEN is reset to 0).
Cleared by hardware at power-up, should not be cleared by the device firmware
once set.
6 - 0 UADD6:0
USB Address Bits
This field contains the default address (0) after power-up or USB bus reset.
It should be written with the value set by a SET_ADDRESS request received by
the device firmware.
7 6 5 4 3 2 1 0
- - WUPCPU EORINT SOFINT - - SPINT
Bit
Number
Bit
Mnemonic Description
7 - 6 -
Reserved
The value read from these bits is always 0. Do not set these bits.
5 WUPCPU
Wake Up CPU Interrupt Flag
Set by hardware when the USB controller is in SUSPEND state and is re-
activated by a non-idle signal from USB line (not by an upstream resume). This
triggers a USB interrupt when EWUPCPU is set in the USBIEN.
Cleared by software after re-enabling all USB clocks.
4 EORINT
End of Reset Interrupt Flag
Set by hardware when a End of Reset has been detected by the USB controller.
This triggers a USB interrupt when EEORINT is set in USBIEN.
Cleared by software.
3 SOFINT
Start of Frame Interrupt Flag
Set by hardware when an USB Start of Frame packet (SOF) has been properly
received. This triggers a USB interrupt when ESOFINT is set in USBIEN.
Cleared by software.
2 - 1 -
Reserved
The value read from these bits is always 0. Do not set these bits.
0 SPINT
Suspend Interrupt Flag
Set by hardware when a USB Suspend (Idle bus for three frame periods: a J
state for 3 ms) is detected. This triggers a USB interrupt when ESPINT is set in
USBIEN.
Cleared by software.