NEC switch - Manual (Page 144)

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