USB5744

DS00001855L-page 16

 2022 Microchip Technology Inc. and its subsidiaries

3.4

Configuration Straps and Programmable Functions

Configuration straps are multi-function pins that are used during Power-On Reset (POR) or external chip reset

(RESET_N) to determine the default configuration of a particular feature. The state of the signal is latched following de-

assertion of the reset. Configuration straps are identified by an underlined symbol name. This section details the various

device configuration straps and associated programmable pin functions.

3.4.1

SPI/SMBUS CONFIGURATION

The SPI/SMBus pins can be configured into one of two functional modes:

• SPI Mode

• SMBus Slave Mode

If 10 k

 pull-up resistors are detected on SPI_DO and SPI_CLK, the SPI/SMBus pins are configured into SMBus Slave

Mode. If no pull-ups or pull-downs are detected on SPI_DO and SPI_CLK, the SPI/SMBus pins are first configured into

SPI Mode. The strap settings for these supported modes are detailed in Table 3-10. The individual pin function assign-

ments for each mode are detailed in Table 3-11. For additional device connection information, refer to Section 4.0,

"Device Connections".

Note 4: In order to use the SPI interface, an SPI ROM containing a valid signature of 2DFU (device firmware

upgrade) beginning at address 0xFFFA must be present. Refer to Section 7.1, "SPI Master Interface" for

additional information.

Note:

The system designer must guarantee that configuration straps meet the timing requirements specified in

Section 10.6.2, "Power-On and Configuration Strap Timing," on page 36 and Section 10.6.3, "Reset and

Configuration Strap Timing," on page 37. If configuration straps are not at the correct voltage level prior to

being latched, the device may capture incorrect strap values.

TABLE 3-10:

SPI/SMBUS MODE CONFIGURATION SETTINGS

Pin

SPI Mode

(Note 4)

SMBus Slave Mode

39

(SPI_DO)

No pull-up/down

10 k

 pull-up

38

(SPI_CLK)

No pull-up/down

10 k

 pull-up

TABLE 3-11:

SPI/SMBUS MODE PIN ASSIGNMENTS

Pin

SPI Mode

SMBus Slave Mode

41

SPI_CE_N

CFG_NON_REM

40

SPI_DI

CFG_BC_EN

39

SPI_DO

SMDAT

38

SPI_CLK

SMCLK