SAF1761BE/V1,557 NXP Semiconductors, SAF1761BE/V1,557 Datasheet - Page 84

• Manufacturer Part Number: SAF1761BE/V1,557
• Manufacturer: NXP Semiconductors

Specifications of SAF1761BE/V1,557

• Lead Free Status / Rohs Status: Compliant

NXP Semiconductors
9. OTG controller
SAF1761_1
Product data sheet
9.1 Introduction
9.2 Dual-role device
OTG is a supplement to the Hi-Speed USB specification that augments existing USB
peripherals by adding to these peripherals limited host capability to support other targeted
USB peripherals. It is primarily targeted at portable devices because it addresses
concerns related to such devices, such as a small connector and low power. Non-portable
devices, even standard hosts, can also benefit from OTG features.
The SAF1761 OTG controller is designed to perform all the tasks specified in the OTG
supplement. It supports Host Negotiation Protocol (HNP) and Session Request Protocol
(SRP) for dual-role devices. The SAF1761 uses software implementation of HNP and
SRP for maximum flexibility. A set of OTG registers provides the control and status
monitoring capabilities to support software HNP and SRP.
Besides the normal USB transceiver, timers and analog components required by OTG are
also integrated on-chip. The analog components include:
When port 1 of the SAF1761 is configured in OTG mode, it can be used as an OTG
dual-role device. A dual-role device is a USB device that can function either as a host or
as a peripheral.
The default role of the SAF1761 is controlled by the ID pin, which in turn is controlled by
the type of plug connected to the micro-AB receptacle. If ID = LOW (micro-A plug
connected), it becomes an A-device, which is a host by default. If ID = HIGH (micro-B plug
connected), it becomes a B-device, which is a peripheral by default.
Both the A-device and the B-device work on a session base. A session is defined as the
period of time in which devices exchange data. A session starts when V
ends when V
During a session, the role of the host can be transferred back and forth between the
A-device and the B-device any number of times by using HNP.
If the A-device wants to start a session, it turns on V
B-device detects that V
of a peripheral asserting its pull-up resistor on the DP line. The A-device detects the
remote pull-up resistor and assumes the role of a host. Then, the A-device can
communicate with the B-device as long as it wishes. When the A-device finishes
communicating with the B-device, the A-device turns off V
into the idle state. See
If the B-device wants to start a session, it must initiate SRP by data line pulsing and
V
(Note: only the A-device is allowed to drive V
•
•
•
•
BUS
Built-in 3.3 V-to-5 V charge pump
Voltage comparators
Pull-up or pull-down resistors on data lines
Charging or discharging resistors for V
pulsing. When the A-device detects any of these SRP events, it turns on its V
BUS
is turned off. Both the A-device and the B-device may start a session.
Rev. 01 — 18 November 2009
BUS
Figure 14
has risen above the B_SESS_VLD level and assumes the role
and
Figure
BUS
15.
BUS
.) The B-device assumes the role of a
BUS
by enabling the charge pump. The
Hi-Speed USB OTG controller
BUS
and both devices finally go
SAF1761
© NXP B.V. 2009. All rights reserved.
BUS
is driven and
84 of 166
BUS
.