NEC switch User Manual page 144

Figure 8-25. Flowchart of Transmit/Receive Pointer Operation (5/7)
(3) Data packet transmit (1/2)
Idle state
Transmit/receive
signal?
Y
Data/handshake transmission
Set USBPOW to 7FH
Set USBPOB to 00H
Bit read
Y
Does bit stuffing
signal = 1?
N
USBPOB increment
N
USBPOB
overflow?
Y
Handshake
Transmit area?
(reservation flag
judgment)
Transmit buffer
Set USBPOW to n0H
1
DTXCO0, DTXCO1: Data packet transmit byte number counter
144
CHAPTER 8
Go to (4)
n = 2: Transmit buffer 0
n = 3: Transmit buffer 1
User's Manual U12978EJ3V0UD
USB FUNCTION
1
m = 0: send buffer 0
m = 1: send buffer 1
Does
USBPOW match
DTXCOm?
N
Bit Read
Y
Does bit stuffing
signal = 1?
N
USBPOB increment
N
USBPOB
overflow?
Y
USBPOW increment
USBPOW
= n1H?
N
Y
2
Y
Set CRC16 execution
start signal