USB3813 datasheet(27/68 Pages) SMSC

27 / 68 page

USB 2.0 Hi-Speed 3-Port Hub Controller Optimized for Portable Applications

Datasheet

SMSC USB3813

Revision 1.0 (06-17-13)

DATASHEET

6.3

Device Configuration Straps

Configuration straps are multi-function pins that are driven as outputs during normal operation. During

a Power-On Reset (POR) or an External Chip Reset (RESET_N), these outputs are tri-stated. The high

or low state of the signal is latched following de-assertion of the reset and is used to determine the

default configuration of a particular feature. Configuration straps are latched as a result of a Power-On

Reset (POR) or a External Chip Reset (RESET_N). Configuration strap signals are noted in Chapter 3,

"Ball Descriptions," on page 10 and are identified by an underlined symbol name. The following sub-

sections detail the various configuration straps.

Configuration straps include internal resistors in order to prevent the signal from floating when

unconnected. If a particular configuration strap is connected to a load, an external pull-up or pull-down

should be used to augment the internal resistor to ensure that it reaches the required voltage level

prior to latching. The internal resistor can also be overridden by the addition of an external resistor.

Note: The system designer must guarantee that configuration straps meet the timing requirements

specified in Section 9.5.2, "Reset and Configuration Strap Timing," on page 63 and Section

9.5.1, "Power-On Configuration Strap Valid Timing," on page 62. If configuration straps are not

at the correct voltage level prior to being latched, the device may capture incorrect strap

values.

Note: Configuration straps must never be driven as inputs. If required, configuration straps can be

augmented, or overridden with external resistors.

6.3.1

SPI Speed Select (SPI_SPD_SEL)

This strap is used to select the speed of the SPI as follows:

Note: If the latched value on reset is 1, this pin is tri-stated when the chip is in the suspend state. If

the latched value on reset is 0, this pin is driven low during a suspend state.

Table 6.1 SPI_SPD_SEL Configuration Definitions

SPI_SPD_SEL

DEFINITION

‘0’

30 MHz SPI Operation (Default)

‘1’

60 MHz SPI Operation

USB3813 数据表(PDF) 27 Page - SMSC Corporation

USB3813 数据表(HTML) 27 Page - SMSC Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

数据表下载