
Universal Serial Bus Interface – On-The-Go Module
21-28
Freescale Semiconductor
Upon discovery of a transmit (OUT/SETUP) packet in the data structures, the host controller checks to
ensure
T
p
remains before the end of the (micro)frame. If so, it pre-fills the TX FIFO. If at anytime during
the pre-fill operation the time remaining the (micro)frame is less than
T
s
, packet attempt ceases and tries
at a later time. Although this is not an error condition and the module eventually recovers, a mark is made
in the scheduler health counter to mark the occurrence of a back-off event. When a back-off event is
detected, the partial packet fetched may need to be discarded from the latency buffer to make room for
periodic traffic beginning after the next SOF. Too many back-off events can waste bandwidth and power
on the system bus and should be minimized (not necessarily eliminated). The TSCHHEALTH (
T
ff
)
parameter described below can minimize back-offs.
Address: 0xFC0B_0164 (TXFILLTUNING)
Access: User read/write
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
R 0
0
0
0
0
0
0
0
0
0
TXFIFOTHRES
0
0
0
TXSCHHEALTH
TXSCHOH
W
Reset 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 21-25. Transmit FIFO Tuning Controls (TXFILLTUNING)
Table 21-28. TXFILLTUNING Field Descriptions
Field
Description
31–22
Reserved, must be cleared.
21–16
TXFIFOTHRES
FIFO burst threshold. Controls the number of data bursts that are posted to the TX latency FIFO in host mode
before the packet begins on the bus. The minimum value is 2 and this value should be as low as possible to
maximize USB performance. Systems with unpredictable latency and/or insufficient bandwidth can use a
higher value where the FIFO may underrun because the data transferred from the latency FIFO to USB
occurs before it can replenish from system memory.
This value is ignored if the USBMODE[SDIS] bit is set. When the USBMODE[SDIS] bit is set, the host
controller behaves as if TXFIFOTHRES is set to its maximum value.
15–13
Reserved, must be cleared.
MCF5329 Reference Manual, Rev 3
Summary of Contents for MCF5329
Page 106: ...ColdFire Core 3 32 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 148: ...Cache 5 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 154: ...Static RAM SRAM 6 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 184: ...Power Management 8 18 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 204: ...Reset Controller Module 10 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 220: ...System Control Module SCM 11 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 228: ...Crossbar Switch XBS 12 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 268: ...General Purpose I O Module 13 40 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 392: ...SDRAM Controller SDRAMC 18 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 436: ...Fast Ethernet Controller FEC 19 44 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 594: ...FlexCAN 23 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 678: ...Pulse Width Modulation PWM Module 26 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 684: ...Watchdog Timer Module 27 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 704: ...DMA Timers DTIM0 DTIM3 29 12 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 754: ...UART Modules 31 34 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 770: ...I2 C Interface 32 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 866: ...Debug Module 36 50 Freescale Semiconductor MCF5329 Reference Manual Rev 3...