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749
USB Controller Module
Register bit assignment
HcFmNumber register
Address: 9010 103C
The HcFmNumber register is a 16-bit counter that provides a timing reference among
events happening in the host controller driver. The host controller driver can use the
16-bit value specified in this register and generate a 32-bit frame number without
requiring frequent access to the register.
Bits Access Mnemonic Reset Description
D31 R FRT 0b FrameRemainingToggle
Loaded from the FrameIntervalToggle field of the
HcFmInterval register (see "HcFmInterval register" on
page 747) when FrameRemaining (D13:00 in this
register) reaches 0.
This bit is used by HCD for synchronization between
FrameInterval and FrameRemaining.
D30:14 N/A Reserved N/A N/A
D13:00 R FR 0h FrameRemaining counter
Decremented at each bit time. When the counter reaches
zero, it is reset by loading the FrameInterval value
specified in the HcFrameInterval register (see
"HcFmInterval register" on page 747) at the next bit time
boundary.
Table 437: HcFmRemaining register
13121110987654321015 14
31 29 28 27 26 25 24 23 22 21 20 19 18 17 1630
Reserved
FrameNumber (FN