CHAPTER 12 USB FUNCTION CONTROLLER (USBF)
Preliminary User’s Manual U19014EJ1V0UD
284
(2) UF0 EP0NAKALL register (UF0E0NA)
This register controls NAK to all the requests of Endpoint0. It is also valid for automatically executed requests.
This register can be read or written in 8-bit units.
0
UF0E0NA
0
5
0
0
3
0
2
0
1
0
EP0NKA
Address
FF61H
After reset
00H
0
4
6
7
Bit position
Bit name
Function
0
EP0NKA
This bit controls NAK to a transaction other than a SETUP transaction to Endpoint0
(including an automatically executed request). This bit is manipulated by FW.
1: Transmit NAK.
0: Do not transmit NAK (default value).
This register is used to prevent a conflict between a write access by FW and a read
access from SIE when the data used for an automatically executed request is to be
changed. It postpones reflecting a write access on this bit from FW while an access
from SIE is being made. Before rewriting the request data register from FW, confirm that
this bit has been correctly set to 1.
Setting this bit to 1 is reflected only in the following cases.
•
Immediately after USBF has been reset and a SETUP token has never been
received
•
Immediately after reception of Bus Reset and a SETUP token has never been
received
•
PID of a SETUP token has been detected
•
The stage has been changed to the status stage
Clearing this bit to 0 is reflected immediately, except while an IN token is being received
and a NAK response is being made.
Setting the EP0NKA bit to 1 is reflected in the above four cases during Endpoint0
transfer, but it is reflected immediately after data has been written to the bit while
Endpoint0 is transferring no data.
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