Cypress Semiconductor FX2LP Informazioni Techniche Pagina 383

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Chapter 15. Registers Page 15-63
15.10 USB Control
15.10.1 USB Control and Status
Figure 15-63. USB Control and Status
Bit 7 HSM High Speed Mode
If HSM=1, the SIE is operating in High Speed Mode, 480 bits/sec. 0-1 transition of this bit
causes a HSGRANT interrupt request.
Bit 3 DISCON Signal a Disconnect on the DISCON
Pin
DISCON is one of the EZ-USB FX2 control bits in the USBCS (USB Control and Status) Reg-
ister that control the ReNumeration process. Setting this bit to 1 will disconnect from the USB
bus by removing the internal 1.5 K pull-up resistor from the D+. A boot EEPROM may be used
to default this bit to 1 at startup time. This bit will also reset several registers. See
Chapter 7
"Resets"
for details.
Bit 2 NOSYNSOF Disable Synthesizing Missing SOFs
If set to 1, disable synthesizing missing SOFs.
Bit 1 RENUM Renumerate
This bit controls whether USB device requests are handled by firmware or automatically by the
FX2. When RENUM=0, the USB core handles all device requests. When RENUM=1, the firm-
ware handles all device requests except Set_Address. Set RENUM=1 during a bus disconnect
to transfer USB control to the firmware. The FX2 automatically sets RENUM=1 under two con-
ditions:
1. Completion of a C2 boot load
2. When external memory is used (EA=1) and no boot EEPROM is used.
USBCS USB Control and Status E680
b7 b6 b5 b4 b3 b2 b1 b0
HSM 0 0 0 DISCON NOSYNSOF RENUM SIGRSUME
R R R R R/W R/W R/W R/W
x 0 0 0 0 0 0 0
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