Freescale Semiconductor MCF5329 Reference Manual page 471

Field
12–8 Scheduler health counter. These bits increment when the host controller fails to fill the TX latency FIFO to the
TXSCHHEALTH level programmed by TXFIFOTHRES before running out of time to send the packet before the next SOF.
This health counter measures the number of times this occurs to provide feedback to selecting a proper
TXSCHOH. Writing to this register clears the counter and this counter stops counting after reaching the
maximum of 31.
7–0 Scheduler overhead. These bits add an additional fixed offset to the schedule time estimator described as T
TXSCHOH As an approximation, the value chosen for this register should limit the number of back-off events captured in
the TXSCHHEALTH field to less than 10 per second in a highly utilized bus. Choosing a value too high for this
register is not desired as it can needlessly reduce USB utilization.
The time unit represented in this register is 1.267 μs when a device connects in high-speed mode.
The time unit represented in this register is 6.333 μs when a device connects in low-/full-speed mode.
For most applications, TXSCHOH can be set to 4 or less. A good value to begin with is:
Always rounded to the next higher integer. TimeUnit is 1.267 or 6.333 as noted earlier in this description. For
example, if TXFIFOTHRES is 5 and BURSTSIZE is 8, set TXSCHOH to 5×(8×4)/(40×1.267) equals 4 for a
high-speed link. If this value of TXSCHOH results in a TXSCHHEALTH count of 0 per second, low the value
by 1 if optimizing performance is desired. If TXSCHHEALTH exceeds 10 per second, raise the value by 1.
If streaming mode is disabled via the USBMODE register, treat TXFIFOTHRES as the maximum value for
purposes of the TXSCHOH calculation.
21.3.3.12 ULPI Register Access (ULPI_VIEWPORT)
The register provides indirect access to the ULPI PHY register set. Although the controller modules
perform access to the ULPI PHY register set, there may be circumstances where software may need direct
access.
Be advised that writes to the ULPI through the ULPI viewport can
substantially harm standard USB operations. Currently no usage model has
been defined where software should need to execute writes directly to the
ULPI. Executing read operations though the ULPI viewport should have no
harmful side effects to standard USB operations. Also, if the ULPI interface
is not enabled, this register is always read cleared.
Address: 0xFC0B_0170 (ULPI_VIEWPORT)
31 30 29
R ULPI_
ULPI_ ULPI_
WU RUN RW
W
Reset 0 0 0
Freescale Semiconductor
Table 21-28. TXFILLTUNING Field Descriptions (continued)
TXFIFOTHRES
------------------------------------------------------------------------------------------- -
28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
0 ULPI_
ULPI_
ULPI_ADDR
SS PORT
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Figure 21-26. ULPI Register Access (ULPI VIEWPORT)
MCF5329 Reference Manual, Rev 3
Universal Serial Bus Interface – On-The-Go Module
Description
× ( × )
BURSTSIZE 4
×
40 TimeUnit
NOTE
ULPI_DATRD
Eqn. 21-1
Access: User read/write
9 8 7 6 5 4 3
ULPI_DATWR
0 0 0 0 0 0 0 0 0 0 0 0
.
ff
2 1 0
21-29