K60P100M100SF2RM Datasheet, PDF (1261/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Chapter 45 Universal Serial Bus OTG Controller (USBOTG)
USBx_TOKEN field descriptions
Field
Description
7–4
TOKENPID
This 4-bit field contains the token type executed by the USB Module.
0001
1001
1101
OUT Token. USB Module performs an OUT (TX) transaction.
IN Token. USB Module performs an In (RX) transaction.
SETUP Token. USB Module performs a SETUP (TX) transaction
3–0
This 4 bit field holds the Endpoint address for the token command. The four bit value written must be a
TOKENENDPT valid endpoint.
45.4.20 SOF Threshold Register (USBx_SOFTHLD)
The SOF Threshold Register is used only in Hosts mode (HOSTMODEEN=1). When in
Host mode, the 14-bit SOF counter counts the interval between SOF frames. The SOF
must be transmitted every 1msec so the SOF counter is loaded with a value of 12000.
When the SOF counter reaches zero, a Start Of Frame (SOF) token is transmitted. The
SOF threshold register is used to program the number of USB byte times before the SOF
to stop initiating token packet transactions. This register must be set to a value that
ensures that other packets are not actively being transmitted when the SOF time counts to
zero. When the SOF counter reaches the threshold value, no more tokens are transmitted
until after the SOF ha been transmitted. The value programmed into the threshold register
must reserve enough time to ensure the worst case transaction completes. In general the
worst case transaction is a IN token followed by a data packet from the target followed by
the response from the host. The actual time required is a function of the maximum packet
size on the bus. Typical values for the SOF threshold are: 64-byte packets=74; 32-byte
packets=42; 16-byte packets=26; 8-byte packets=18.
Addresses: USB0_SOFTHLD is 4007_2000h base + ACh offset = 4007_20ACh
Bit
7
6
5
4
3
2
1
0
Read
Write
CNT
Reset
0
0
0
0
0
0
0
0
USBx_SOFTHLD field descriptions
Field
7–0
CNT
Description
This 8-bit field represents the SOF count threshold in byte times.
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
1261