NEC switch User Manual page 132

(3) Control transfer (IN) (Transfer byte count: 8 bytes or less)
Packet flow
Packet from
host controller
SETUP
Setup
stage
DATA0
IN
Data
stage IN
reception
ACK
OUT
DATA1
Status
stage OUT
reception
OUT
reception
wait
Note If the ACK from the device cannot be received normally, the host transmits OUT again. Therefore, set
the OUT receive wait state for a period so that the OUT can be received. Use a normal 8-bit timer for
counting during this period.
132
CHAPTER 8 USB FUNCTION
Packet from
Operation of host
µ
PD789800
controller
ACK
DATA1
ACK
User's Manual U12978EJ3V0UD
Request
IN packet
OUT packet
USB communication
Note
completion timer timeout
Operation of USB
µ
function of PD789800
ACK transmission
reservation
• ACK transmission
• DATA1 transmission
reservation
• DATA1 transmission
• NAK transmission
reservation
NAK transmission
reservation clear
ACK transmission
reservation
• ACK transmission
• USB communication
completion timer
start
NAK transmission
reservation