AT43USB325 datasheet(71/109 Pages) ATMEL

71 / 109 page

3355C–USB–4/05

AT43USB325

8.2

USB Registers

The following sections describe the registers of the AT43USB325’s USB hub and function units.

Reading a bit for which the microcontroller does not have read access will yield a zero value

result. Writing to a bit for which the microcontroller does not have write access has no effect.

8.2.1

Hub Address Register – HADDR

The USB hub contains an address register that contains the hub address assigned by the host.

This Hub Address Register must be programmed by the microcontroller once it has received a

SET_ADDRESS request from the host. The USB hardware uses the new address only after the

status phase of the transaction is completed when the microcontroller has enabled the new

address by setting bit 0 of the Global State Register. After power-up or reset, this register will

contain the value of 0x00.

8.2.1.1

Hub Address Register – HADDR

• Bit 7 – SAEN: Single Address Enable

The Single Address Enable bit allows the microcontroller to configure the AT43USB325 into a

single address or a composite device. Once this capability is enabled, the hub endpoint 0

(HEP0) is converted from a control endpoint to a programmable function endpoint FEP3; all the

endpoints would then operate on the single address.

• Bit 6..0 – HADD6...0: Hub Address[6:0]

8.2.2

Function Address Register – FADDR

The USB function contains an address register that contains the function address assigned by

the host. This Function Address Register must be programmed by the microcontroller once it

has received a SET_ADDRESS request from the host and completed the status phase of the

transaction. After power up or reset, this register will contain the value of 0x00.

8.2.2.1

Function Address Register – FADDR

• Bit 7 – FEN: Function Enable

The Function Enable bit (FEN) allows the firmware to enable or disable the function endpoints.

The firmware will set this bit after receipt of a reset through the hub, SetPortFea-

ture[PORT_RESET]. Once this bit is set, the USB hardware passes to and from the host.

When the Single Address bit is set, the condition of FEN is ignored.

• Bit 6..0 – FADD6...0: Function Address[6:0]

Bit

$1FEF

SAEN

HADD6

HADD5

HADD4

HADD3

HADD2

HADD1

HADD0

HADDR

Read/Write

R/W

Initial Value

Bit

$1FEE

FEN

FADD6

FADD5

FADD4

FADD3

FADD2

FADD1

FADD0

FADDR

Read/Write

R/W

Initial Value

AT43USB325 데이터시트(PDF) 71 Page - ATMEL Corporation

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