NEC switch User Manual
Page 117
CHAPTER 8 USB FUNCTION
User’s Manual U12978EJ3V0UD
117
Figure 8-16. Format of Handshake Packet Transmit Reservation Register (2/2)
ACKEN
ACK packet transmit reservation flag after data packet reception
0
1
No data is transmitted.
ACK handshake is transmitted when all the following conditions are satisfied in EOP during data packet reception.
DIDRST = 1, DBYER = 0, DBITER = 0, CR16ER = 0
E0NAEN
NAK packet transmit reservation flag for Endpoint 0 after IN packet
0
1
No data is transmitted.
NAK handshake is transmitted when all the following conditions are satisfied in EOP during IN packet reception.
INRX (internal signal) = 1, TIDRST = 1, ADRRST = 1, END0RX = 0, TBYER = 0, TBITER = 0, CRC5ER = 0
DNAEN
NAK packet transmit reservation flag after data packet reception
0
1
No data is transmitted.
If all the following conditions are met, NAK handshake is transmitted in EOP during data packet reception.
Set this flag when saving data from reception data addresses (USBR0 to USBR7).
OUTRX (internal signal) = 1, DIDRST = 1, DBYER = 0, DBITER = 0, CR16ER = 0, UWDERR = 0
E1NAEN
NAK packet transmit reservation flag for Endpoint 1 after IN packet
0
1
No data is transmitted.
NAK handshake is transmitted when all the following conditions are satisfied in EOP during IN packet reception.
INRX (internal signal) = 1, ADRRST = 1, END1RX = 1, TBYER = 0, TBITER = 0, CRC5ER = 0
During transmit reservation, all the conditions listed in Table 8-3 below must be satisfied.
Table 8-3. Conditions in Transmit Reservation (1/2)
(a) Transmit reservation for Endpoint 0 and IN token packet
Type of Reservation
DT00EN
DT10EN
E0STEN
E0NAEN
Transmit reservation of data in transmit buffer 0
1
0
0
0
Transmit reservation of data in transmit buffer 1
0
1
0
0
Endpoint 0 STALL transmit reservation
(occurrence of length error, or halt status)
0
0
1
0
Endpoint 0 NAK transmit reservation
(data creation incomplete)
0
0
0
1
Two or more reservations above
Setting prohibited