Usb Function Internal Circuit Operations; Operation Of Transmit/Receive Pointer; Flowchart Of Transmit/Receive Pointer Operation - NEC switch User Manual

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)
Idle state
Transmit/receive
signal?
Y
Token reception
Set USBPOW to 00H
Set USBPOB to 00H
EOP
Bit normal write?
Y
Y
Does bit stuffing
signal = 1?
N
USBPOB increment
N
USBPOB
overflow?
Y
USBPOW increment
Y
USBPOW
= 01H?
N
N
USBPOW
= 02H?
Y
1
TBYER: Bit 5 of token packet receive result store register (TRXRSL)
140
CHAPTER 8 USB FUNCTION
Set TBYER flag
Idle state
Set CRC5 execution
start signal
User's Manual U12978EJ3V0UD
1
EOP
Bit normal write?
Y
Y
Does bit stuffing
signal = 1?
N
USBPOB increment
N
USBPOB
= 02H?
Y
EOP
Bit normal write?
N
Y
Does bit stuffing
signal = 1?
N
Set USBPOW to 70H
Set USBPOB to 00H
2
Set TBYER flag
Idle state
Set TBYER flag
Idle state