USB3803 datasheet(20/99 Pages) MICROCHIP

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USB3803

DS00001691B-page 20

 2014-2015 Microchip Technology Inc.

5.0

CONFIGURATION OPTIONS

5.1

Hub Configuration Options

The Hub supports a number of features (some are mutually exclusive), and must be configured in order to correctly func-

tion when attached to a USB host controller. There are two principal ways to configure the hub: by writing to configuration

registers using the serial slave port, or by internal default settings. Any configuration registers which are not written by

the serial slave retain their default settings.

5.1.1

MULTI/SINGLE TT

The USB 2.0 Hub is fully specification compliant to the Universal Serial Bus Specification Revision 2.0 April 27,2000

(12/7/2000 and 5/28/2002 Errata). Please reference Chapter 11 (Hub Specification) for general details regarding Hub

operation and functionality.

For performance reasons, the Hub provides 1 Transaction Translator (TT) per port (defined as Multi-TT configuration),

and each TT has 1512 bytes of periodic buffer space and 272 Bytes of non- periodic buffer space (divided into 4 non-

periodic buffers per TT), for a total of 1784 bytes of buffer space for each Transaction Translator.

When configured as a Single-TT Hub (required by USB 2.0 Specification), the Single Transaction Translator will have

1512 bytes of periodic buffer space and 272 bytes of non-periodic buffer space (divided into 4 non-periodic buffers per

TT), for a total of 1784 bytes of buffer space for the entire Transaction Translator. Each Transaction Translator’s buf-

fer is divided as shown in

Table 5-1, "Transaction Translator Buffer Chart".

5.1.2

VBUS DETECT

According to Section 7.2.1 of the USB 2.0 Specification, a downstream port can never provide power to its D+ or D- pull-

up resistors unless the upstream port's VBUS is in the asserted (powered) state. Depending on input tie-offs and values

in the configuration registers, the USB3803 may automatically enable the D+ pull-up resistor once it enters the Hub.Con-

nect stage of Hub Mode (after RESET_N and BYPASS_N (USB3803C Only) are both negated high.) To fully adhere

to the USB specification, the system should not cause the part to enter Hub.Com Hub Mode until VBUS has been

detected on the upstream port and a connection is desired.

5.2

Default Serial Interface Register Memory Map

The Serial Interface Registers are used to customize the USB3803 for specific applications. Reserved registers or

reserved bits within a defined register should not be written to non-default values or undefined behavior may result.

TABLE 5-1:

TRANSACTION TRANSLATOR BUFFER CHART

Periodic Start-Split Descriptors

256 Bytes

Periodic Start-Split Data

752 Bytes

Periodic Complete-Split Descriptors

128 Bytes

Periodic Complete-Split Data

376 Bytes

Non-Periodic Descriptors

16 Bytes

Non-Periodic Data

256 Bytes

Total for each Transaction Translator

1784 Bytes

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