USB224X

DS00001979A-page 26

 2010 - 2015 Microchip Technology Inc.

7.2.5.7

D3h: Dynamic Number of LUNs

7.2.5.8

D4h-D7h: Device to LUN Mapping

7.2.5.9

D8h-FBh: Not Applicable

7.2.5.10

FCh-FFh: Non-Volatile Storage Signature

7.3

Default Configuration Option

The Microchip device can be configured via its internal default configuration. Please see Section 7.2.2, "EEPROM Data

Descriptor" for specific details on how to enable default configuration. Please refer to Table 7-1 for the internal default

values that are loaded when this option is selected.

7.3.1

EXTERNAL HARDWARE RESET_N

A valid hardware reset is defined as assertion of RESET_N for a minimum of 1

μs after all power supplies are within

operating range. While reset is asserted, the device (and its associated external circuitry) consumes less than 500

μA

of current from the upstream USB power source.

Assertion of RESET_N (external pin) causes the following:

1.

The PHY is disabled and the differential pair will be in a high-impedance state.

2.

All transactions immediately terminate; no states are saved.

3.

All internal registers return to the default state.

4.

The external crystal oscillator is halted.

5.

The PLL is halted.

6.

The processor is reset.

7.

All media interfaces are reset.

Bit

Name

Description

7:0

DYN_NUM_LUN

These bytes are used to specify the number of LUNs the device exposes to

the host. These bytes are also used for icon sharing by assigning more than

one LUN to a single icon. This is used in applications where the device utilizes

a combo socket and the OEM wishes to have only a single icon displayed for

one or more interfaces.

If this field is set to "FF", the program assumes that you are using the default

value and icons will be configured per the default configuration.

Byte

Name

Description

3:0

DEV_LUN_MAP

These registers map a device controller (SD/MMC, SM, and MS) to a Logical

Unit Number (LUN). The device reports the mapped LUNs to the USB host in

the USB descriptor during enumeration. The icon installer associates custom

icons with the LUNs specified in these fields.

Setting a register to "FF" indicates that the device is not mapped. Setting all

of the DEV_LUN_MAP registers for all devices to "FF" forces the use of the

default mapping configuration. Not all configurations are valid. Valid

configurations depend on the hardware, packaging, and OEM board layout.

The number of unique LUNs mapped must match the value in the Section

7.2.5.7, "D3h: Dynamic Number of LUNs," on page 26.

Byte

Name

Description

35:0

Not Applicable

Not Applicable.

Byte

Name

Description

3:0

NVSTORE_SIG

This signature is used to verify the validity of the data in the first 256 bytes of

the configuration area. The signature must be set to ‘ATA2’ for USB224x.