SN8F2250B Series
USB 2.0 Full-Speed 8-Bit Micro-Controller
9.5.6 USB endpoint’s NAK handshaking flag REGISTER
The status of endpoint’s NAK transaction.
095H
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
EP3_NAK EP2_NAK EP1_NAK
EP_NAK
Read/Write
After reset
R/W
0
R/W
0
R/W
0
Bit [2:0] EPn_NAK [2:0]: EP1~EP3 NAK transaction. n = 1, 2, 3. The bit is set whenever the endpoint that
completes with an NAK received.
0 = the EPnNAK_INT_EN = 0 or the endpoint (interrupt pipe) doesn’t complete with an NAK.
1 = the EPnNAK_INT_EN = 1 and the endpoint (interrupt pipe) complete with an NAK.
9.5.7 USB ENDPOINT 0 ENABLE REGISTER
An endpoint 0 (EP0) is used to initialize and control the USB device. EP0 is bi-directional (Control pipe), as the device,
can both receive and transmit data, which provides to access the device configuration information and allows generic
USB status and control accesses.
096H
UE0R
Read/Write
After reset
Bit 7
Bit 6
UE0M1
R/W
0
Bit 5
UE0M0
R/W
0
Bit 4
Bit 3
UE0C3
R/W
0
Bit 2
UE0C
R/W
0
Bit 1
UE0C1
R/W
0
Bit 0
UE0C0
R/W
0
-
-
-
-
-
-
Bit [3:0] UE0C [3:0]: Indicate the number of data bytes in a transaction: For IN transactions, firmware loads the
count with the number of bytes to be transmitted to the host from the endpoint 0 FIFO.
Bit [6:5] UE0M [1:0]: The endpoint 0 modes determine how the SIE responds to USB traffic that the host sends to
the endpoint 0. For example, if the endpoint 0’s mode bit is set to 00 that is NAK IN/OUT mode as shown in
Table, The USB SIE will send NAK handshakes in response to any IN/OUT token set to the endpoint 0.The
bit 5 UE0M0 will auto reset to zero when the ACK transaction complete.
USB endpoint 0’s mode table
UE0M1
UE0M0
IN/OUT Token Handshake
0
0
1
1
0
1
0
1
NAK
ACK
STALL
STALL
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