13 usb frame number register (frmnumr), Usb frame number register (frmnumr) -21 – Freescale Semiconductor MCF5480 User Manual
Page 895
Memory Map/Register Definition
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor
29-21
29.2.2.13 USB Frame Number Register (FRMNUMR)
29.2.2.14 USB Endpoint Transaction Number Register (EPTNR)
The EPTNR is used for high-speed, high-bandwidth, isochronous IN endpoints only. It contains the
number of transactions required by the endpoint in the next microframe.
The EPTNR is used to provide information to the USB 2.0 device controller regarding the number of IN
transactions needed to deliver data in the next microframe. Following the pre-buffering model specified in
the USB Specification, Rev 2.0, the data to be transmitted in the next microframe is gathered in the current
microframe (see section 5.9.2 of the USB Specification, Rev. 2.0). Therefore, by the end of the current
microframe, the USB application is aware of the number of IN transactions required to convey the newly
gathered data to the host. This is the number that needs to be written into the appropriate field of this
register.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
0
0
FRMNUM
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Reg
Addr
MBAR + 0xB00E
Figure 29-14. USB Frame Number Register (FRMNUMR)
Table 29-14. FRMNUMR Field Descriptions
Bits
Name
Description
16–12
—
Reserved, should be cleared.
11–0
FRMNUM
This register contains the frame number of an SOF packet and is updated each time an
SOF packet is received. FRMNUM can range from 0x000 through 0x7FF.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
0
0
EP6T
EP5T
EP4T
EP3T
EP2T
EP1T
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Reg
Addr
MBAR + 0xB010
Figure 29-15. Endpoint Transaction Number Register (EPTNR)