2 usb control register (usbcn), 3 usb configuration register (usbcfg) – Maxim Integrated MAXQ622 User Manual
Page 176
MAXQ612/MAXQ622 User’s Guide
12-6
Maxim Integrated
12.4.2 USB Control Register (USBCN)
Bit 7: Oscillator Start (OSCST). Setting this bit to 1 allows the USB controller to enable the oscillator when USB bus
activity is detected on D+ (host resume signaling) . Clearing this bit to 0 keeps the USB controller in low-power state
(inhibit the oscillator from starting) when the USB host resumes bus signaling .
Bit 6: VBUS Gate (VBGATE). Setting this bit to 1 makes operation of the CONNECT bit conditional on VBUS being
present on the VBUS pin . Clearing this bit to 0 makes operation of the CONNECT bit independent of VBUS being valid .
Bit 5: USB Controller Reset (URST). Setting this bit to 1 resets all the USB controller internal states and USB regis-
ters (excluding the USBCN register) to their respective default values . This bit remains set unless cleared by software .
Bit 4: USB Power-Down (PWRDN). Setting this bit to 1 instructs the USB controller to enter a low-power state required
by a USB peripheral in the suspended state . Clearing this bit to 0 takes the USB controller out of the low-power state
and resumes operation .
Bit 3: Connect to USB (CONNECT). Setting this bit to 1 requests the external transceiver to connect an internal 1500I
resistor between the D+ line and V
CC
. Clearing this bit to 0 disconnects the external transceiver internal 1500I resistor
between the D+ line and V
CC
. This goes to the ENUM output pin .
Bit 2: Signal USB Remote Wake-Up (SIGRWU). Setting this bit to 1 signals remote wake-up to the host .
Bits 1 and 0: Reserved. Reads returns zero.
12.4.3 USB Configuration Register (USBCFG)
Note: This register is initialized on POR only.
Note: This register is initialized on POR only.
Bits 7 to 1: Reserved. Reads returns zero.
Bit 0: USB Enable (USBEN). Setting this bit to 1 enables the USB controller . Clearing this bit to 0 disables the USB
controller . Once disabled, the device does not respond to any USB traffic, regardless of the setting in the other USB
register . This bit is cleared following a POR and is unaffected by all other resets .
Register Name
USBCN
Register Description
USB Control Register
Register Address
UADDR[4:0] = 02h
Register Name
USBCFG
Register Description
USB Configuration Register
Register Address
UADDR[4:0] = 03h
Bit #
7
6
5
4
3
2
1
0
Name
OSCST
VBGATE
URST
PWRDN
CONNECT
SIGRWU
—
—
Reset
1
0
1
1
0
0
0
0
Access
rw
rw
rw
rw
rw
rw
rw
rw
Bit #
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
—
—
USBEN
Reset
0
0
0
0
0
0
0
0
Access
rw
rw
rw
rw
rw
rw
rw
rw