RM0082
HS_USB2.0 host
Doc ID 018672 Rev 1
431/844
22.6.11 FRINDEX
register
The FRINDEX (frame index) is a RW register used by the EHCI host controller to index into
the periodic frame list. The register updates every 125 microseconds, that is each micro-
frame. The FRINDEX register bit assignments are given in
Note:
1
The FRINDEX register must be written as a DWord. Byte writes produce undefined results.
2
The FRINDEX register cannot be written unless the EHCI host controller is in the halted
state as indicated by the HCHalted bit (in USBSTS register). A write to this register while the
RS bit (in USBCMD register) is set to 0b1 produces undefined results. Writes to this register
also affect the SOF value.
The value of the frame index field increments at the end of each time frame (e.g. micro-
frame). In particular, bits [N:3] of this field are used as frame list current index to select a
particular entry in the periodic frame list during periodic schedule execution.
Note:
This means that each location of the frame list is accessed 8 times (frames or micro-frames)
before moving to the next index.
The actual number of bits (that is, N) used for the frame list current index depends on the
size of the frame list as set by system software in the FLS field in the USBCMD register,
according to encoding:
[02]
Port Change
Interrupt Enable
1‘h0
When both this bit and the port change detect (PGD)
bit in the USBSTS register are set, the EHCI host
controller will issue an interrupt.
The interrupt is acknowledged by software clearing
the PGD bit.
[01]
USB Error
Interrupt Enable
1‘h0
When both this bit and the USBERRINT bit in the
USBSTS register are set, the EHCI host controller will
issue an interrupt at the next interrupt threshold. The
interrupt is acknowledged by software clearing the
USBERRINT bit.
[00]
USB Interrupt
Enable
1‘h0
When both this bit and the USBINT bit in the
USBSTS register are set, the EHCI host controller will
issue an interrupt at the next interrupt threshold. The
interrupt is acknowledged by software clearing the
USBINT bit.
Table 356.
USBINTR register bit assignments (continued)
Bit
Name
Reset value Description
Table 357.
FRINDEX register bit assignments
Bit
Name
Reset value Description
[31:14]
Reserved
-
Read: undefined. Write: should be zero.
[13:00]
Frame Index
14‘h0000
See