42.4.18 Frame Number register High (USBx_FRMNUMH)
The Frame Number registers (low and high) contain the 11-bit frame number. These
registers are updated with the current frame number whenever a SOF TOKEN is
received.
Address: 4007_2000h base + A4h offset = 4007_20A4h
Bit
7
6
5
4
3
2
1
0
Read
Write
Reset
0
0
0
0
0
0
0
0
USBx_FRMNUMH field descriptions
Field
Description
7–3
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
2–0
FRM[10:8]
This 3-bit field and the 8-bit field in the Frame Number Register Low are used to compute the address
where the current Buffer Descriptor Table (BDT) resides in system memory.
42.4.19 Token register (USBx_TOKEN)
Used to initiate USB transactions when in host mode (HOSTMODEEN=1). When the
software needs to execute a USB transaction to a peripheral, it writes the TOKEN type
and endpoint to this register. After this register has been written, the USB module begins
the specified USB transaction to the address contained in the address register. The
processor core must always check that the TOKEN_BUSY bit in the control register is
not 1 before writing to the Token Register. This ensures that the token commands are not
overwritten before they can be executed. The address register and endpoint control
register 0 are also used when performing a token command and therefore must also be
written before the Token Register. The address register is used to select the USB
peripheral address transmitted by the token command. The endpoint control register
determines the handshake and retry policies used during the transfer.
Address: 4007_2000h base + A8h offset = 4007_20A8h
Bit
7
6
5
4
3
2
1
0
Read
Write
Reset
0
0
0
0
0
0
0
0
Memory map/Register definitions
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
1016
Freescale Semiconductor, Inc.
