C8051F340/1/2/3/4/5/6/7
16.6. Function Addressing
The FADDR register holds the current USB0 function address. Software should write the host-assigned
7-bit function address to the FADDR register when received as part of a SET_ADDRESS command. A new
address written to FADDR will not take effect (USB0 will not respond to the new address) until the end of
the current transfer (typically following the status phase of the SET_ADDRESS command transfer). The
UPDATE bit (FADDR.7) is set to ‘1’ by hardware when software writes a new address to the FADDR regis-
ter. Hardware clears the UPDATE bit when the new address takes effect as described above.
USB Register Definition 16.7. FADDR: USB0 Function Address
R
R/W
Bit6
R/W
Bit5
R/W
Bit4
R/W
R/W
Bit2
R/W
Bit1
R/W
Bit0
Reset Value
Update
Bit7
Function Address
Bit3
00000000
USB Address:
0x00
Bit7:
Update: Function Address Update
Set to ‘1’ when software writes the FADDR register. USB0 clears this bit to ‘0’ when the new
address takes effect.
0: The last address written to FADDR is in effect.
1: The last address written to FADDR is not yet in effect.
Bits6–0: Function Address
Holds the 7-bit function address for USB0. This address should be written by software when
the SET_ADDRESS standard device request is received on Endpoint0. The new address
takes effect when the device request completes.
16.7. Function Configuration and Control
The USB register POWER (SFR Definition 16.8) is used to configure and control USB0 at the device level
(enable/disable, Reset/Suspend/Resume handling, etc.).
USB Reset:
The USBRST bit (POWER.3) is set to ‘1’ by hardware when Reset signaling is detected on
the bus. Upon this detection, the following occur:
1. The USB0 Address is reset (FADDR = 0x00).
2. Endpoint FIFOs are flushed.
3. Control/status registers are reset to 0x00 (E0CSR, EINCSRL, EINCSRH, EOUTCSRL,
EOUTCSRH).
4. USB register INDEX is reset to 0x00.
5. All USB interrupts (excluding the Suspend interrupt) are enabled and their corresponding flags
cleared.
6. A USB Reset interrupt is generated if enabled.
Writing a ‘1’ to the USBRST bit will generate an asynchronous USB0 reset. All USB registers are reset to
their default values following this asynchronous reset.
Suspend Mode:
With Suspend Detection enabled (SUSEN = ‘1’), USB0 will enter Suspend Mode when
Suspend signaling is detected on the bus. An interrupt will be generated if enabled (SUSINTE = ‘1’). The
Suspend Interrupt Service Routine (ISR) should perform application-specific configuration tasks such as
disabling appropriate peripherals and/or configuring clock sources for low power modes. See
Rev. 1.0
177
SILABS [ SILICON LABORATORIES ]
