Endpoint Control X Register (Epc1 To Epc6); Transmit Status X Register (Txs1, Txs2, Txs3) - NS USBN9603 Manual

7.0 Register Set
(Continued)

7.2.20 Endpoint Control X Register (EPC1 to EPC6)

Each unidirectional endpoint has an EPCx register with the bits defined below.
bit 7
STALL
0
r/w
EP
Endpoint. This field holds the 4-bit endpoint address.
EP_EN
Endpoint Enable. When this bit is set, the EP3-0 field is used in address comparison, together with the AD6-0 field in the
FAR register. See Section 6.2 for a description. When cleared, the endpoint does not respond to any token on the USB bus.
Note: AD_EN in the FAR register is the global address compare enable for the device. If it is cleared, the device does not
respond to any address, regardless of the EP_EN state.
ISO
Isochronous. When this bit is set to 1, the endpoint is isochronous. This implies that no NAK is sent if the endpoint is not
ready but enabled; i.e. if an IN token is received and no data is available in the FIFO to transmit, or if an OUT token is re-
ceived and the FIFO is full since there is no USB handshake for isochronous transfers.
STALL
Setting this bit causes the chip to generate STALL handshakes under the following conditions:
1. The transmit FIFO is enabled and an IN token is received.
2. The receive FIFO is enabled and an OUT token is received.
Setting this bit does not generate a STALL handshake in response to a SETUP token.

7.2.21 Transmit Status X Register (TXS1, TXS2, TXS3)

Each of the three transmit endpoint FIFOs has a Transmit Status register with the bits defined below.
bit 7
TX_URUN
0
CoR
TCOUNT
Transmission Count. This bit indicates the count of empty bytes available in the FIFO. If this count is greater than 31, a value
of 31 is reported.
TX_DONE
Transmission Done. When set, this bit indicates that the endpoint responded to a USB packet. Three conditions can cause
this bit to be set:
1. A data packet completed transmission in response to an IN token with non-ISO operation.
2. The endpoint sent a STALL handshake in response to an IN token
3. A scheduled ISO frame was transmitted or discarded.
This bit is cleared when this register is read.
ACK_STAT
Acknowledge Status. This bit is interpreted when TX_DONE is set. Its function differs depending on whether ISO (ISO in the
EPCx register is set) or non-ISO operation (ISO is reset) is used.
For non-ISO operation, this bit indicates the acknowledge status (from the host) about the ACK for the previously sent pack-
et. This bit itself is set when an ACK is received; otherwise, it is cleared.
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bit 6 bit 5 bit 4
Reserved ISO EP_EN
- 0
- r/w r/w
bit 6 bit 5
ACK_STAT TX_DONE
0
CoR CoR
bit 3 bit 2
EP3-0
0 0 0
bit 4 bit 3
TCOUNT4-0
0 0 0
46
bit 1 bit 0
0 0
r/w
bit 2 bit 1 bit 0
0 0 0
r