USB251XB datasheet(13/57 Pages) MICROCHIP

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DS00001692D-page 13

USB251xB/xBi

SERIAL PORT INTERFACES

SDA/

I/OSD12

Serial Data Signal

SMBDATA/

System Management Bus Signal

NON_REM1

Non-Removable Port 1 Strap Option: when enabled by package and configuration

options (see Table 5-1 on page 19), this pin will be sampled (in conjunction with

LOCAL_PWR/SUSP_IND/NON_REM0) at RESET_N negation to determine if

ports [x:1] contain permanently attached (non-removable) devices:

NON_REM[1:0] = 00 : all ports are removable

NON_REM[1:0] = 01 : port 1 is non-removable

NON_REM[1:0] = 10 : ports 1 and 2 are non-removable

NON_REM[1:0] = 11 : when available, ports 1, 2, and 3 are non-removable

When NON_REM[1:0] is chosen such that there is a non-removable device, the

hub will automatically report itself as a compound device (using the proper

descriptors).

RESET_N

RESET Input: the system can reset the chip by driving this input low. The

minimum active low pulse is 1

s.

SCL/

I/OSD12

Serial Clock (SCL)

SMBCLK/

System Management Bus Clock

CFG_SEL0

Configuration Select: the logic state of this multifunction pin is internally latched

on the rising edge of RESET_N (RESET_N negation), and will determine the hub

configuration method as described in Table 5-1.

HS_IND/

I/O12

Hi-Speed Upstream Port Indicator: upstream port connection speed.

Asserted = the hub is connected at HS

Negated = the hub is connected at FS

Note:

When implementing an external LED on this pin, the active state is

indicated above and outlined in Section 3.3.1.3, on page 15.

CFG_SEL1

Configuration Programming Select 1: the logic state of this pin is internally latched

on the rising edge of RESET_N (RESET_N negation), and will determine the hub

configuration method as described in Table 5-1.

MISC

XTALIN

ICLKx

Crystal Input: 24 MHz crystal.

This pin connects to either one terminal of the crystal or to an external 24 MHz

clock when a crystal is not used.

CLKIN

External Clock Input: this pin connects to either one terminal of the crystal or to

an external 24 MHz clock when a crystal is not used.

XTALOUT

OCLKx

Crystal Output: this is the other terminal of the crystal circuit with 1.2 V p-p output

and a weak (< 1mA) driving strength. When an external clock source is used to

drive XTALIN/CLKIN, leave this pin unconnected, or use with appropriate

caution.

TABLE 3-2:

USB251XB/XBI PIN DESCRIPTIONS (CONTINUED)

Symbol

Buffer

Type

Description

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