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CHAPTER 6 USB CONTROLLER
Preliminary User’s Manual S14767EJ1V0UM00
377
6.2.2 Explanation of registers
This section explains each bit field of the address-mapped registers.
6.2.2.1 USB General Mode Register (U_GMR): 00H
Reserved
SOFINTVL
31
16
15
0
RR
3
2
1
LE
7
8
Reserved
AU
FA
23
22
24
VT
This register is used for setting the operation of USB Controller. The low-order eight bits can be written to once
only when the device is being initialized. If the values of these bits are changed while sending or receiving is being
performed, the operation of USB Controller may become unpredictable.
Bit
Field
Description
R/W
31-24
Reserved
Reserved for future use
R
23
VT
(Function Address
Valid Timing)
If this bit is 1, FA become valid immediately.
If this bit is 0, FA will become valid after USB Controller receives
subsequent ACK packet on EndPoint0.
R/W
22-16
FA
(Function Address)
Register that stores the USB Function Address. This is allocated by the
Host PC as part of the USB configuration process. The V
R
4120A RISC
Processor sets the allocated address in this register.
R/W
15-8
SOFINTVL
(SOF Interval)
This value is used to define the allowable skew for SOF packet. The default
value should be 18H.
R/W
7-3
Reserved
Reserved for future use
R
2
AU
(Auto Update)
Frame Number auto update enable.
If this bit is set, Frame Number Register will be updated though SOF packet
is corrupted.
R/W
1
LE
(Loopback Enable)
Bit for enabling internal loopback mode.
When this bit is set to 1, USB Controller operates in loopback mode.
Setting loopback mode enables the testing of the internal DMA controller
that is built into USB Controller.
When loopback mode is set, USB packets are not output. Also, USB
packets are not received.
For a detailed explanation of loopback mode, see Section 6.8.
R/W
0
RR
(Remote Resume)
When Remote Resume is to be performed, the V
R
4120A RISC Processor
sets this bit.
Once this bit has been set, USB Controller issues Resume Signaling to the
USB for a period of 5 ms. Upon the completion of Resume Signaling, this
bit is automatically reset to 0.
R/W