USBN9603 National Semiconductor, USBN9603 Datasheet - Page 46

• Manufacturer Part Number: USBN9603
• Description: USBN9603 Universal Serial Bus Full Speed Function Controller with Enhanced DMA Support
• Manufacturer: National Semiconductor

www.national.com
7.0 Register Set
7.2.20 Endpoint Control X Register (EPC1 to EPC6)
Each unidirectional endpoint has an EPCx register with the bits defined below.
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 USBN9603. 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.
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.
STALL
bit 7
TX_URUN
r/w
0
bit 7
CoR
0
(Continued)
Reserved
bit 6
-
-
ACK_STAT
bit 6
CoR
0
bit 5
ISO
r/w
0
TX_DONE
EP_EN
bit 4
CoR
bit 5
r/w
0
0
46
bit 3
bit 4
0
0
bit 3
0
bit 2
0
TCOUNT4-0
EP3-0
r/w
bit 2
0
r
bit 1
0
bit 1
0
bit 0
bit 0
0
0