HS_USB 2.0 device
RM0082
502/844
Doc ID 018672 Rev 1
23.8.14
Endpoint maximum packet size and buffer size register
This is an endpoint-specific RW register which gives both the buffer size in the RxFIFO
associated to an out endpoint, and the maximum packet size an endpoint (both in and out)
should support. This maximum packet size is used to calculate whether the RxFIFO has
sufficient space to accept a packet. The register bit assignments are given in
.
Note:
When the maximum packet size for a specific endpoint is changed, the application must also
properly set the UDC register space.
[17:16]
ISO PID
(IN/OUT)
2’h0
Initial data PID to be sent for a high-bandwidth ISO
transaction.
For IN
These 2 bits indicate the initial data PID to be transmitted for
an high-bandwidth ISO transaction, according to encoding:
– 2‘b00 = DATA0.
– 2‘b01 = DATA0.
– 2‘b10 = DATA1.
– 2‘b11 = DATA2.
For OUT,
These 2 bits indicate the initial data PID of the packet
received (that is, available in the RxFIFO) for an high-
bandwidth ISO transaction, according to encoding:
– 2'b00 = DATA0.
– 2'b01 = DATA1.
– 2'b10 = DATA2.
– 2'b11 = MDATA.
Note: The ISO PID field is used in slave-only mode, and it is
reserved for the UDC11.
[15:00]
BUFF SIZE
(IN)
16’h0000
For IN
Buffer size required for this endpoint.
This 16 bit field represents the size of the buffer associated
to that in endpoint as an integer number of 32 bit words.
Resulting flexibility in buffer size allows the application to
cope with interface or configuration changes.
For OUT
Frame number in which the packet is received.
This 16 bit field states the frame number in which an
incoming packet has been received by the RxFIFO for that
out endpoint, as follows:
-High-Speed (HS) operation
[15:14] Reserved.
[13:3] Millisecond frame number.
[2:0] Micro-frame number.
Full-Speed (FS) operation
[15:11] Reserved.
[10:0] Millisecond frame number
Table 409.
Endpoint buffer size/received packet frame number register bit
assignments (continued)
Bit
Name
Reset value Description