Usb Real-Time Frame Monitor Register (Rfmr) - Motorola DigitalDNA ColdFire MCF5272 User Manual

Register Description and Programming Model
Bits Name
15–11 — Reserved, should be cleared
10–0 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.

12.3.2.3 USB Real-Time Frame Monitor Register (RFMR)

The value in the RFMR can be used to determine approximately how much time has
elapsed since the USB host sent its last start-of-frame packet.
Because the hardware does not guarantee that any of the bit values are stable during the read
access:
• only the higher-order bits should be used
• the returned data should always be de-glitched by verifying that the same value is
seen on the higher-order bits for two consecutive read cycles.
Figure 12-5 shows the USB real-time frame monitor register.
15 14
Field —
Reset
R/W
Addr
Figure 12-5. USB Real-Time Frame Monitor Register (RFMR)
Table 12-5 lists field descriptions for the USB real-time frame monitor register.
Bits Name
15–14 — Reserved, should be cleared.
13–0 RTFM Real-time frame count. Contains the current USB frame counter value. The counter is
incremented one time for every USB bit time and is reset when a SOF packet from the
host is detected or an artificial start of frame (ASOF) interrupt is generated.
12.3.2.4 USB Real-Time Frame Monitor Match Register (RFMMR)
To avoid intermediate false values in the real-time frame monitor match register
Figure 12-6 byte accesses are not supported and cause an access error.
,
12-10
Table 12-4. FNMR Field Descriptions
13
0000_0000_0000_0000
MBAR + 0x100A
Table 12-5. RFMR Field Descriptions
MCF5272 User's Manual
Description
RTFM
Read
Description
0
,