MCF5272CVM66 Datasheet, PDF (267/544 Pages) Freescale Semiconductor, Inc – MCF5272 ColdFire® Integrated Microprocessor

12.3.2 Register Descriptions
The following are detailed register diagrams and field descriptions.
Universal Serial Bus (USB)
12.3.2.1 USB Frame Number Register (FNR)
Once every 1 ms, the USB host issues a start-of-frame packet containing a frame number. The FNR register
captures this frame number. Figure 12-3 shows the FNR.
15
11 10
0
Field
—
FRM
Reset
0000_0000_0000_0000
R/W
Read
Addr
MBAR + 0x1002
Figure 12-3. USB Frame Number Register (FNR)
Table 12-3 describes FNR fields.
Table 12-3. FNR Field Descriptions
Bits
15–11
10–0
Name
Description
—
FRM
Reserved, should be cleared.
USB frame number. Contains the current USB frame number. FRM is updated with the new frame number
each time the device successfully receives a start-of-frame (SOF) packet from the USB host. The new frame
number is contained in the SOF packet.
12.3.2.2 USB Frame Number Match Register (FNMR)
FNMR is used to signal, via the FRM_MAT interrupt, when a particular frame number is issued by the
USB host. To avoid a false match during intermediate states of a byte write operation to the FNMR,
Figure 12-4, byte accesses to this register are not supported and cause an access error.
15
11 10
0
Field
—
FRM_MAT
Reset
0000_0000_0000_0000
R/W
R/W
Addr
MBAR + 0x1006
Figure 12-4. USB Frame Number Match Register (FNMR)
Table 12-4 describes FNMR fields.
Table 12-4. FNMR Field Descriptions
Bits
15–11
10–0
Name
Description
—
Reserved, should be cleared
FRM_MAT Frame number match value. Contains the USB frame number match value. When the FNR value equals
the value in the register, a FRM_MAT interrupt is generated.
MCF5272 ColdFire^® Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
12-9