Method and system for high-speed detection handshake in universal serial bus based data communication system
View Patent ↗A USB system includes a USB hub, a USB device, and a USB bus interconnecting the USB hub and the USB device. The USB hub asserts a reset signaling on the USB bus to initiate a high-speed detection handshake. The USB hub and the USB device activate corresponding dual-mode squelch detectors in a first (handshake) mode of operation. The USB device transmits a device chirp signal to the USB hub. The USB hub responds with a sequence of hub chirp signals. The USB device detects the hub chirp signals and then the USB hub and the USB device establish a communication link in a high-speed mode of communication in accordance with USB 2.0. The dual-mode squelch detectors in the USB hub and the USB device can also be activated in a second (normal) mode of operation.
1. A method for high-speed detection handshake between a first transceiver and a second transceiver connected with a USB bus, the USB bus comprising a first data line (DP) and a second data line (DM), the method comprising:
asserting a reset signaling at the USB bus that drives the first and second data lines to a first voltage level for a predefined time interval at the first transceiver;
activating a dual-mode squelch detector in each of the first transceiver and the second transceiver in a first mode of operation, wherein the dual-mode squelch detectors in the first mode of operation generate a squelch signal based on a differential signal received from the USB bus, wherein the squelch signal is in a first predefined state when the differential signal is below a first threshold voltage level and in a second predefined state when the differential signal exceeds a second threshold voltage level;
initiating a chirp signaling between the first transceiver and the second transceiver;
enabling a high-speed communication mode in the first and the second transceivers based on successful completion of the chirp signaling; and
activating the dual-mode squelch detectors in each of the first and second transceivers in a second mode of operation, wherein the dual-mode squelch detectors in the second mode of operation generate a squelch signal based on the differential signal received from the USB bus, wherein the squelch signal is in the first predefined state when the differential signal is below a third threshold voltage level, and in the second predefined state when the differential signal exceeds a fourth threshold voltage level.
2. The method for high-speed detection handshake of claim 1 , wherein when the reset signaling is asserted, an operational mode of the first transceiver switches from a current state to a first predefined state.
3. The method for high-speed detection handshake of claim 1 , further comprising detecting the reset signaling at the second transceiver.
4. The method for high-speed detection handshake of claim 3 , wherein when the reset signaling is detected, an operational mode of the second transceiver switches from a current state to a first predefined state.
5. The method for high-speed detection handshake of claim 1 , wherein the dual-mode squelch detectors in each of the first and second transceivers are activated in the first mode of operation when an operational mode of the first and the second transceivers is in a first predefined state.
6. The method for high-speed detection handshake of claim 1 , wherein the first and second threshold voltage levels in the first mode of operation are based on an offset voltage present on the first and second data lines during the high-speed detection handshake.
7. The method for high-speed detection handshake of claim 1 , wherein the chirp signaling comprises:
asserting a device chirp signal on the USB bus; and
asserting an alternating sequence of a first hub chirp and a second hub chirp on the USB bus.
8. The method for high-speed detection handshake of claim 1 , wherein the dual-mode squelch detectors in each of the first and second transceivers are activated in the second mode of operation when an operational mode of the first and the second transceivers is in a second predefined state.
9. The method for high-speed detection handshake of claim 1 , wherein the first threshold voltage level in the first mode of operation is selected from a range of voltages varying from about 190 mV to about 210 mV, and the second threshold voltage level in the first mode of operation is selected from a range of voltages varying from about 220 mV to about 250 mV.
10. The method for high-speed detection handshake of claim 1 , wherein the third threshold voltage level in the second mode of operation is 100 mV, and the fourth threshold voltage level in the second mode of operation is 150 mV.
11. The method for high-speed detection handshake of claim 1 , wherein a full-speed communication mode is enabled on the first and second transceivers based on unsuccessful completion of chirp signaling.
12. A USB system, comprising:
a first transceiver including,
a full-speed driver for asserting a reset signaling that drives first and second data lines to a first predefined voltage level for a predefined time interval;
a first dual-mode squelch detector for generating a first squelch signal, wherein the first dual-mode squelch detector is operable in two modes;
a first differential receiver for detecting a device chirp signal; and
a first high-speed current driver for generating a sequence of hub chirp signals;
a second transceiver including,
a second high-speed current driver for generating the device chirp signal;
a second differential receiver for detecting the reset signaling and the sequence of hub chirp signals; and
a second dual-mode squelch detector for generating a second squelch signal, wherein the second dual-mode squelch detector is operable in two modes; and
a USB bus connecting the first transceiver and the second transceiver, wherein the USB bus comprises the first and second data lines, wherein,
each of the first and the second dual-mode squelch detectors generates a squelch signal based on a differential signal received from the USB bus,
each of the first and the second dual-mode squelch detectors is operable in a first mode of operation,
the squelch signal is in a first predefined state when the differential signal is below a first threshold voltage level,
the squelch signal is in a second predefined state when the differential signal exceeds a second threshold voltage level,
each of the first and the second dual-mode squelch detectors is operable in a second mode of operation,
the squelch signal is in the first predefined state when the differential signal is below a third threshold voltage level, and
the squelch signal is in the second predefined state when the differential signal exceeds a fourth threshold voltage level.
13. The USB system of claim 12 , wherein each of the first data line and the second data line are connected to a high-speed driver termination network at the first transceiver and to a full-speed driver termination network at the second transceiver, and wherein the first data line is connected to a pull-up resistor of the full-speed driver termination network at the second transceiver.
14. The USB system of claim 12 , wherein the dual-mode squelch detector is activated in the first mode of operation when an operational mode of the first and the second transceivers is in a first predefined state.
15. The USB system of claim 12 , wherein the dual-mode squelch detector is activated in the second mode of operation when an operational mode of the first transceiver is in a second predefined state.
16. The USB system of claim 12 , wherein the first and second threshold voltage levels in the first mode of operation are based on an offset voltage present on the first and second data lines during the high-speed detection handshake.
17. The USB system of claim 12 , wherein the first threshold voltage level in the first mode of operation is selected from a range of voltages varying from about 190 mV to about 210 mV, and wherein the second threshold voltage level in the first mode of operation is selected from a range of voltages varying from about 230 mV to about 250 mV.
18. The USB system of claim 12 , wherein the third threshold voltage level in the second mode of operation is 100 mV and the fourth threshold voltage level in the second mode of operation is 150 mV.