Cypress Semiconductor FX2LP Información técnica Pagina 127

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Chapter 6. Power Management Page 6-5
Once in the low-power mode, there are three ways to wake up the FX2:
USB activity on the FX2’s DPLUS pin
Assertion of the WAKEUP pin
Assertion of the WU2 (“Wakeup 2”) pin
These three wakeup sources may be individually enabled by setting the DPEN, WUEN, and
WU2EN bits in the Wakeup Control register.
The polarities of the wakeup pins are set using the WUPOL and WU2POL bits; 0 is active low and
1 is active high.
Three bits in the WAKEUP register enable the three wakeup sources. DPEN stands for “DPLUS
Enable” (DPLUS is one of the USB data lines; the other is DMINUS).
WUEN (Wakeup Enable) enables the WAKEUP pin, and WU2EN (Wakeup 2 Enable) enables the
WU2 pin.
When the FX2 chip detects activity on DPLUS while DPEN is true, or a false-to-true transition on
WAKEUP or WU2 while WUEN or WU2EN is true, it asserts the “wakeup” interrupt.
The status bits WU and WU2 indicate which of the wakeup pins caused the wakeup event. Assert-
ing the wakeup pin (according to its programmed polarity) sets the corresponding bit. If the wakeup
was caused by resumption of USB DPLUS activity, neither of these bits is set, leading to the con-
clusion that the third source, a USB bus reset, caused the wakeup event. FX2 firmware clears the
WU and WU2 flags by writing “1” to them.
6.3.1 Wakeup Interrupt
When a wakeup event occurs, the FX2 restarts its oscillator and, after the PLL stabilizes, it gener-
ates an interrupt request. This applies whether or not the FX2 is connected to the USB. The
Wakeup Interrupt is a dedicated interrupt, and is not shared by USBINT like most of the other indi-
vidual USB interrupts.
The Wakeup Interrupt vector is at 0x33, and has the highest interrupt priority. It is enabled by
EICON.5, and its IRQ flag is at EICON.4 (EICON is SFR 0xD8).
WAKEUPCS Wakeup Control & Status E682
b7 b6 b5 b4 b3 b2 b1 b0
WU2 WU WU2POL WUPOL 0 DPEN WU2EN WUEN
R/W R/W R/W R/W R R/W R/W R/W
0 0 0 0 0 1 0 1
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