Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 862

Universal Serial Bus (USB)
1 2
Offset Name
0x1C TXUSBU_PTR
0x1E —
1
Offset from endpoint parameter block base.
2
Note that the items in boldface should be initialized by the user.
3
These parameters need not be accessed in normal operation but may be helpful for debugging.
31.10.1 Frame Number (FRAME_N)
This entry is used for frame number updates both in function mode and in host mode. In function mode it
is updated by the USB controller, in host mode it is updated by the application software.
31.10.1.1 Frame Number in Function Mode
This entry is updated by the USB controller in function mode whenever a SOF (start of frame) token is
received. The entry contains 11 bits that represent the frame number. An SOF interrupt is issued upon an
update of this entry.
0 1
1
Field V
Reset
R/W
Addr
1
This bit is set if the SOF token was received error free.
Table 31-5 describes FRAME_N fields.
Bits Name
0 V
1–4 —
5–15 FRAME NUMBER
31.10.1.2 Frame Number In Host Mode
The entry is updated by the application software whenever a SOF (start of frame) token should be received.
The software should prepare the frame number and the crc and place it in FRAME_N field.
31-14
Table 31-4. Endpoint Parameter Block (continued)
Width
16 bits Tx microcode return address temp
16 bits Reserved
4 5
—
0000_0000_0000_0000
Figure 31-9. Frame Number (FRAME_N) in Function mode
Table 31-5. FRAME_N Field Descriptions
The valid bit is set if the SOF token is received without error.
Reserved, should be cleared.
The frame number is loaded with the value received in the SOF packet. Be sure the
frame number is cleared before beginning USB operation.
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Description
FRAME NUMBER
R/W
USB base + 0x10
Description
15
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