USBN9603 National Semiconductor, USBN9603 Datasheet - Page 49

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

7.0 Register Set
For ISO operation, this bit reflects the LSB of the frame number (FNL0) after a packet was successfully received for this
endpoint.
This bit is reset to 0 by reading the RXSx register.
SETUP
This bit indicates that the setup packet has been received. It is cleared when this register is read.
RX_ERR
Receive Error. When set, this bit indicates a media error, such as bit-stuffing or CRC. If this bit is set, the firmware must flush
the respective FIFO.
7.2.25 Receive Command X Register (RXC1, RXC2, RXC3)
Each of the receive endpoints (2, 4 and 6) has one Receive Command register with the bits defined below.
RX_EN
Receive Enable. OUT packet cannot be received after every data packet is received, or when a STALL handshake is re-
turned in response to an OUT token. This bit must be written with a 1 to re-enable data reception. SETUP packets can always
be received. In the case of back-to-back SETUP packets (for a given endpoint) where a valid SETUP packet has been re-
ceived with no other intervening non-SETUP tokens, the receive state machine discards the new SETUP packet and returns
an ACK handshake. If, for any other reason, the receive state machine cannot accept the SETUP packet, no HANDSHAKE
should be generated.
IGN_SETUP
Ignore SETUP Tokens. When this bit is set, the endpoint ignores any SETUP tokens directed to its configured address.
FLUSH
Writing a 1 to this bit flushes all data from the corresponding receive FIFO, resets the endpoint to Idle state, and resets both
the FIFO read and write pointers. If the MAC is currently using the FIFO to receive data, flushing is delayed until after re-
ceiving is completed.
RFWL1-0
Receive FIFO Warning Limit. These bits specify how many more bytes can be received to the respective FIFO before an
overrun condition occurs. If the number of empty bytes remaining in the FIFO is equal to or less than the selected warning
limit, the RXWARN bit in the FWEV register is set.
Reserved
bit 7
-
-
(Continued)
bit 6
RFWL1-0
0
r/w
bit 5
0
0
1
1
RFWL Bits
1
0
Table 9. Set Receive FIFO Warning Limit
Reserved
bit 4
-
-
0
1
0
1
0
FLUSH
bit 3
Bytes Remaining in FIFO
r/w
49
0
RFWL disabled
IGN_SETUP
16
4
8
bit 2
r/w
0
Reserved
bit 1
-
-
RX_EN
bit 0
r/w
0
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