Nxp Semiconductors UM10237 用户手册
UM10237_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 19 December 2008
368 of 792
NXP Semiconductors
UM10237
Chapter 13: LPC24XX USB device controller
11.10 Select Endpoint (Command: 0x00 - 0x1F, Data: read 1 byte (optional))
The Select Endpoint command initializes an internal pointer to the start of the selected
buffer in EP_RAM. Optionally, this command can be followed by a data read, which
returns some additional information on the packet(s) in the endpoint buffer(s). The
command code of the Select Endpoint command is equal to the physical endpoint
number. In the case of a single buffered endpoint the B_2_FULL bit is not valid.
buffer in EP_RAM. Optionally, this command can be followed by a data read, which
returns some additional information on the packet(s) in the endpoint buffer(s). The
command code of the Select Endpoint command is equal to the physical endpoint
number. In the case of a single buffered endpoint the B_2_FULL bit is not valid.
Table 354. Select Endpoint Register bit description
Bit
Symbol
Value Description
Reset
value
value
0
FE
Full/Empty. This bit indicates the full or empty status of the
endpoint buffer(s). For IN endpoints, the FE bit gives the
ANDed result of the B_1_FULL and B_2_FULL bits. For OUT
endpoints, the FE bit gives ORed result of the B_1_FULL and
B_2_FULL bits. For single buffered endpoints, this bit simply
reflects the status of B_1_FULL.
endpoint buffer(s). For IN endpoints, the FE bit gives the
ANDed result of the B_1_FULL and B_2_FULL bits. For OUT
endpoints, the FE bit gives ORed result of the B_1_FULL and
B_2_FULL bits. For single buffered endpoints, this bit simply
reflects the status of B_1_FULL.
0
0
For an IN endpoint, at least one write endpoint buffer is empty.
1
For an OUT endpoint, at least one endpoint read buffer is full.
1
ST
Stalled endpoint indicator.
0
0
The selected endpoint is not stalled.
1
The selected endpoint is stalled.
2
STP
SETUP bit: the value of this bit is updated after each
successfully received packet (i.e. an ACKed package on that
particular physical endpoint).
successfully received packet (i.e. an ACKed package on that
particular physical endpoint).
0
0
The STP bit is cleared by doing a Select Endpoint/Clear
Interrupt on this endpoint.
Interrupt on this endpoint.
1
The last received packet for the selected endpoint was a
SETUP packet.
SETUP packet.
3
PO
Packet over-written bit.
0
0
The PO bit is cleared by the ‘Select Endpoint/Clear Interrupt’
command.
command.
1
The previously received packet was over-written by a SETUP
packet.
packet.
4
EPN
EP NAKed bit indicates sending of a NAK. If the host sends an
OUT packet to a filled OUT buffer, the device returns NAK. If
the host sends an IN token packet to an empty IN buffer, the
device returns NAK.
OUT packet to a filled OUT buffer, the device returns NAK. If
the host sends an IN token packet to an empty IN buffer, the
device returns NAK.
0
0
The EPN bit is reset after the device has sent an ACK after an
OUT packet or when the device has seen an ACK after sending
an IN packet.
OUT packet or when the device has seen an ACK after sending
an IN packet.
1
The EPN bit is set when a NAK is sent and the interrupt on NAK
feature is enabled.
feature is enabled.
5
B_1_FULL
The buffer 1 status.
0
0
Buffer 1 is empty.
1
Buffer 1 is full.