NEC switch - 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