
EZ-USB FX2 Technical Reference Manual
Page 15-66 EZ-USB FX2 Technical Reference Manual v2.1
Bit 6 S Set Data Toggle to DATA1
After selecting the desired endpoint by writing the endpoint select bits (IO and EP3:0), set S=1
to set the data toggle to DATA1. The endpoint selection bits should not be changed while this
bit is written.
Bit 5 R Set Data Toggle to DATA0
Set R=1 to set the data toggle to DATA0. The endpoint selection bits should not be changed
while this bit is written.
Bit 4 IO Select IN or OUT Endpoint
Set this bit to select an endpoint direction prior to setting its R or S bit. IO=0 selects an OUT
endpoint, IO=1 selects an IN endpoint.
Bit 3-0 EP3:0 Select Endpoint
Set these bits to select an endpoint prior to setting its R or S bit. Valid values are 0, 1, 2, 4, 6,
and 8.
15.10.5 USB Frame Count High
Figure 15-67. USB Frame Count HIGH
Bit 2-0 FC10:8 High Bits for USB Frame Count
Every millisecond the host sends a SOF token indicating “Start Of Frame,” along with an 11-bit
incrementing frame count. The EZ-USB FX2 copies the frame count into these registers at
every SOF. One use of the frame count is to respond to the USB SYNC_FRAME Request. If
the USB core detects a missing or garbled SOF, it generates an internal SOF and increments
USBFRAMEL-USBRAMEH.
USBFRAMEH USB Frame Count HIGH E684
b7 b6 b5 b4 b3 b2 b1 b0
0 0 0 0 0 FC10 FC9 FC8
R R R R R R R R
0 0 0 0 0 x x x
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