Datasheet

© 2008 Fairchild Semiconductor Corporation www.fairchildsemi.com
FUSB2805 • Rev. 1.0.3 23
FUSB2805 — USB2.0 High-Speed OTG Transceiver with ULPI Interface
V
BUS
Voltage State Encoding
As mentioned in Table 9, changes in the V
BUS
state
encoding initiate an RXCMD to the link. For the link to
receive V
BUS
state updates, the link must first enable the
corresponding interrupts in the USB_INTR_EN_R and
USB_INTR_EN_F registers. Link uses the indicator
signals to take action based on typical configurations
(host, peripheral, OTG device). Table 12 shows the
V
BUS
indicators in RXCMD based on the configuration.
Table 12. V
BUS
Indicator Signals in RXCMD
Configuration
A_VBUS_
VLD
SESS_
VLD
SESS_
END
Standard Host
Yes
No
No
Standard
Peripheral
No
Yes
No
OTG A-Device
Yes
Yes
No
OTG B-Device
No
Yes
Yes
For the standard USB host controller application, the
following applies:
 The system must be able to provide 500 mA
for 4.75 V ≤ V
BUS
≤ 5.25 V.
 An external circuit is to be used to detect over-
current conditions. If the external over-current detector
provides a digital fault signal, the signal must be
connected to the FAULT input pin and the link must do
the following:
1. Set the IND_COMPL bit in the INTF_CTRL
register to 0b or 1b, depending on the polarity
of the external fault signal.
2. Set the USE_EXT_VBUS_IND bit in the
OTG_CTRL register to 1b.
3. If it is not necessary to qualify the fault
indicator with the internal A_VBUS_VLD
comparator, set the IND_PASSTHRU bit in the
INTF_CTRL register to 1b.
For the standard USB peripheral controller
applications, the standard peripherals detect when
V
BUS
is at a sufficient level for operation. SESS_VLD
must be enabled to detect the start and end of a
USB peripheral operation. Detection of the
A_VBUS_VLD and SESS_END thresholds is not
needed for standard peripherals.
For a device configured as an OTG B-device, SESS_VLD
must be used to detect when V
BUS
is at a sufficient level
for operation. SESS_END must be used to detect when
V
BUS
has dropped to a LOW level, allowing the B-device
to safely initiate V
BUS
pulsing SRP.
A device configured as an OTG A-device must provide
a minimum of 8 mA onto V
BUS
. This 8 mA (minimum) is
provided external to the FUSB2805. If the external
charge pump source provides more than 100 mA, the
over-current circuit must be used and the host controller
application criteria apply. The OTG A-device also uses
SESS_VLD to detect when an OTG B-device is initiating
V
BUS
pulsing SRP. The control of this external charge
pump is accomplished via the PSW pin.
RxEvent Encoding
As mentioned in Table 9, this encoding provides
information to the link related to the packets received on
the USB bus. The primary encodings are RxActive,
RxError, and HostDisconnect.
RxActive
When the FUSB2805 detects a SYNC pattern on the
USB bus, it signals an RxActive event to the link. This
RxActive event can be communicated in two methods:
 FUSB2805 simultaneously asserts DIR and NXT; or
 FUSB2805 sends an RXCMD to the link with the
RxActive field in the RxEvent bits set to 1b.
The link must be capable of detecting both methods
and the RxActive frames the receive packet from the
first byte to the last byte. It also must assume that
RxActive is set to 0b when indicated in an RXCMD or
when DIR is de-asserted, whichever occurs first.
The RxActive is also used by the link to time the high-
speed packets and ensure that the bus turn-around
times are met.
RxError
When the FUSB2805 detects an error while receiving a
USB packet, it de-asserts NXT and sends an RXCMD
with the RxError field set to 1b. The received packet is
no longer valid and must be dropped by the link.
HostDisconnect
This encoding is only valid when the FUSB2805 is
configured as a host (DP_PULLDOWN=
DM_PULLDOWN=1b) and indicates to the host
controller when a peripheral is connected (0b) or
disconnected (1b). The host controller must enable
HostDisconnect by setting the HOST_DISCON_R and
HOST_DISC_F bits in the USB_INTR_EN_R and
USB_INTR_EN_F registers, respectively. Changes in
HostDisconnect cause the FUSB2805 to send an
RXCMD to the link with the updated value.
In peripheral mode, HostDisconnect must be ignored
and must not mask events on RxActive or RxError.
Refer to ULPI specifications, section 3.8.1 for details on
RXCMD and TXCMD operations and functionality.