USB3500

DS00002103A-page 26

6.2

OPMODES

The OPMODE[1:0] pins allow control of the operating modes.

The OPMODE[1:0] signals are normally changed only when the transmitter and the receiver are quiescent, i.e. when

entering a test mode or for a device initiated resume.

When using OPMODE[1:0] = 10, the SYNC and EOP patterns are not transmitted.

The only exception to this is when OPMODE[1:0] is set to 10 while TXVALID has been asserted (the transceiver is trans-

mitting a packet), in order to flag a transmission error. In this case, the USB3500 has already transmitted the SYNC

pattern so upon negation of TXVALID the EOP must also be transmitted to properly terminate the packet. Changing the

OPMODE[1:0] signals under all other conditions (while the transceiver is transmitting or receiving data) will generate

undefined results.

6.3

Test Mode Support

6.4

SE0 Handling

For FS operation, IDLE is a J state on the bus. SE0 is used as part of the EOP or to indicate reset. When asserted in

an EOP, SE0 is never asserted for more than 2 bit times. The assertion of SE0 for more than 2.5us is interpreted as a

reset by the device operating in FS mode.

For HS operation, IDLE is a SE0 state on the bus. SE0 is also used to reset a HS device. A HS device cannot use the

2.5us assertion of SE0 (as defined for FS operation) to indicate reset since the bus is often in this state between packets.

If no bus activity (IDLE) is detected for more than 3ms, a HS device must determine whether the downstream facing

port is signaling a suspend or a reset. The following section details how this determination is made. If a reset is signaled,

the HS device will then initiate the HS Detection Handshake protocol.

TABLE 6-3:

OPERATIONAL MODES

Mode[1:0]

State Name

Description

00

Normal Operation

Transceiver operates with normal USB data encoding and decoding

01

Non-Driving

Allows the transceiver logic to support a soft disconnect feature which tri-

states both the HS and FS transmitters, and removes any termination from

the USB making it appear to an upstream port that the device has been

disconnected from the bus

10

Disable Bit Stuffing

and NRZI encoding

Disables bitstuffing and NRZI encoding logic so that 1's loaded from the DATA

bus become 'J's on the DP/DM and 0's become 'K's

11

Reserved

N/A

TABLE 6-4:

USB 2.0 TEST MODES

USB 2.0 Test Modes

USB3500 Setup

Operational Mode

Link Transmitted Data

XCVRSELECT &

TERMSELECT

SE0_NAK

State 0

No transmit

HS

J

State 2

All '1's

HS

K

State 2

All '0's

HS

Test_Packet

State 0

Test Packet data

HS