NEC switch - Manual (Page 146)

CHAPTER 8 USB FUNCTION
User’s Manual U12978EJ3V0UD
146
Figure 8-25. Flowchart of Transmit/Receive Pointer Operation (7/7)
(4) Handshake packet transmission
Y
Y
Handshake
Transmit buffer
Y
N
N
1
Y
Y
N
N
1
Idle state
Set USBPOW to 7FH
USBPOB increment
Set USBPOW to n0H
Set USBPOB to 00H
Bit read
Transmit/receive
signal?
Does bit stuffing
signal = 1?
USBPOB
overflow?
Transmit area?
(reservation flag
judgment)
USBPOB
overflow?
Bit read
USBPOB increment
Set EOP
transmit signal
Idle state
Does bit stuffing
signal = 1?
Data/handshake transmission
Go to (3)
n = 4: ACK
n = 5: NAK
n = 6: STALL