AT43USB325 datasheet(67/109 Pages) ATMEL

67 / 109 page

3355C–USB–4/05

AT43USB325

8.1.4

No-data Status Response State

The Function Interface Unit receives an IN token from the Host. The FIU responds with a zero

length DATA1 packet until receiving an ACK from the host, then asserts a TX_COMPLETE

interrupt.

8.1.5

Control Read Data Response State

The Function Interface Unit receives an IN token from the Host. The FIU responds with NAKs

until TX_PACKET_READY is set. The FIU then sends the data in the FIFO upstream, retrying

un til it succes s fully r e ceive s a n ACK fr om th e hos t. Finally, the FIU cle a rs th e

TX_PACKET_READY bit and asserts a TX_COMPLETE interrupt.

Hardware

Firmware

IN token from Host

Send DATA1(0)

ACK from Host

Set TX COMPLETE

→ INT

Read UISR

Read CSR0

If SET ADDRESS, program the

new Address, set ADD_EN bit

Clear TX_COMPLETE, clear Data

End, set Force STALL in CAR0

Set UIAR[EP0 INTACK]

Hardware

Firmware

IN token from Host

a. If TX Packet Ready = 1, send

DATA0/DATA1

b. If TX Packet Ready = 0, send

NAK

ACK from Host

Clear TX Packet Ready

Set TX Complete

→ INT

Read UISR

Read CSR0

Clear TX COMPLETE in CAR0:

a. If more data: fill FIFO, set TX

Packet Ready, set DIR in CAR0

b. If no more data: set Force

STALL, set DATA END in CAR0

Set UIAR[EP0 INTACK] to clear

interrupt source

Repeat steps 1 through 8

AT43USB325 Datasheet(PDF) 67 Page - ATMEL Corporation

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