Freescale Semiconductor MCF54455 Reference Manual page 247

Universal Serial Bus Interface – On-The-Go Module
Field
1 VBUS charge. Setting this bit causes the VBUS line to charge. This is used for VBus pulsing during SRP.
VC
0 VBUS discharge. Setting this bit causes VBUS to discharge through a resistor.
VD
10.3.4.16 USB Mode Register (USBMODE)
This register is not defined in the EHCI specification. It controls the operating mode of the module.
Address: 0xFC0B_01A8 (USBMODE)
31 30 29
R 0 0 0
W
Reset 0 0 0
15 14 13
R 0 0 0
W
Reset 0 0 0
Field
31–5 Reserved, must be cleared.
4 Stream disable.
SDIS 0 Inactive.
1 Active.
Host mode:
Setting this bit ensures that overruns/underruns of the latency FIFO are eliminated for low bandwidth systems
where the RX and TX buffers are sufficient to contain the entire packet. Enabling stream disable also has the
effect of ensuring the TX latency fills to capacity before the packet launches onto the USB.
Time duration to pre-fill the FIFO becomes significant when stream disable is active. See TXFILLTUNING to
characterize the adjustments needed for the scheduler when using this feature.
Also, in systems with high system bus utilization, setting this bit ensures no overruns or underruns during
operation at the expense of link utilization. SDIS can be left clear and the rules under the description of the
TXFILLTUNING register can limit underruns/overruns for those who desire optimal link performance.
Device mode:
Setting this bit disables double priming on RX and TX for low bandwidth systems. This mode ensures that when
the RX and TX buffers are sufficient to contain an entire packet that the standard double buffering scheme is
disabled to prevent overruns/underruns in bandwidth limited systems.
In high-speed mode, all packets received are responded to with a NYET handshake when stream disable is
active.
3 Setup lockout mode. For the module in device mode, this bit controls behavior of the setup lock mechanism. See
SLOM Section 10.5.3.4.4, "Control Endpoint Operation."
0 Setup lockouts on.
1 Setup lockouts off (software requires use of the USBCMD[SUTW] bit).
10-40
Table 10-34. OTGSC Field Descriptions (continued)
28 27 26 25
0 0 0 0
0 0 0 0
12 11 10 9
0 0 0 0
0 0 0 0
Figure 10-32. USB Mode Register (USBMODE)
Table 10-35. USBMODE Field Descriptions
Description
24 23 22 21
0 0 0 0
0 0 0 0
8 7 6 5
0 0 0 0
SDIS SLOM
0 0 0 0
Description
Access: User read/write
20 19 18 17
0 0 0 0
0 0 0 0
4 3 2 1
ES CM
0 0 0 0
Freescale Semiconductor
16
0
0
0
0