mcf5272 Freescale Semiconductor, Inc, mcf5272 Datasheet - Page 270

• Manufacturer Part Number: mcf5272
• Description: Mcf5272 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

Register Description and Programming Model
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:
Figure 12-5 shows the USB real-time frame monitor register.
Table 12-5 lists field descriptions for the USB real-time frame monitor register.
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
12-10
15–11
10–0
Bits
• only the higher-order bits should be used
• the returned data should always be de-glitched by verifying that the same value is
15–14
13–0
Bits
seen on the higher-order bits for two consecutive read cycles.
FRM_MAT Frame number match value. Contains the USB frame number match value. When the FNR
Reset
Name
Field
Addr
R/W
—
Name
RTFM Real-time frame count. Contains the current USB frame counter value. The counter is
,
Figure 12-5. USB Real-Time Frame Monitor Register (RFMR)
—
byte accesses are not supported and cause an access error.
15
—
Reserved, should be cleared
value equals the value in the register, a FRM_MAT interrupt is generated.
Reserved, should be cleared.
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.
14
13
Table 12-4. FNMR Field Descriptions
Table 12-5. RFMR Field Descriptions
MCF5272 User’s Manual
0000_0000_0000_0000
MBAR + 0x100A
Read
Description
Description
RTFM
MOTOROLA
0
,