NEC switch - Manual (Page 140)

CHAPTER 8 USB FUNCTION
User’s Manual U12978EJ3V0UD
140
8.8 USB Function Internal Circuit Operations
8.8.1 Operation of transmit/receive pointer
Figure 8-25. Flowchart of Transmit/Receive Pointer Operation (1/7)
(1) Token packet reception (1/2)
Y
Y
Y
N
N
Y
Y
EOP
Y
N
N
1
Y
Y
N
N
Y
EOP
Y
N
N
EOP
1
2
Idle state
Set USBPOW to 00H
USBPOB increment
USBPOW increment
Set USBPOB to 00H
Transmit/receive
signal?
Does bit stuffing
signal = 1?
USBPOB
overflow?
USBPOW
= 01H?
USBPOW
= 02H?
USBPOB
= 02H?
Bit normal write?
USBPOB increment
Set USBPOW to 70H
Set USBPOB to 00H
Does bit stuffing
signal = 1?
Does bit stuffing
signal = 1?
Bit normal write?
Bit normal write?
Token reception
Set TBYER flag
Set CRC5 execution
start signal
Idle state
Set TBYER flag
Idle state
Set TBYER flag
Idle state
TBYER: Bit 5 of token packet receive result store register (TRXRSL)