NEC switch - Manual (Page 130)

CHAPTER 8 USB FUNCTION
User’s Manual U12978EJ3V0UD
130
8.7 USB Function Control
8.7.1 Relationship between packets and operation modes
The relationship between packets and operation modes in the USB function is as follows.
(1) Control transfer (OUT) (Transfer byte count: 8 bytes or less)
Request
Operation of host
controller
OUT packet
SETUP
DATA0
ACK
Packet from
host controller
Packet from
PD789800
Setup
stage
Data
stage OUT
reception
IN
ACK
OUT
DATA1
DATA1
ACK
• ACK transmission
• NAK transmission
reservation
Operation of USB
function of PD789800
ACK transmission
reservation
• NAK transmission
reservation clear
• ACK transmission
reservation
• ACK transmission
• DATA1 transmission
reservation
IN packet
DATA1 transmission
NAK transmission
reservation
Status
stage IN
reception
Packet flow
ACK packet
µ
µ