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Figure 33: Slide switch S2 (angle view).
Figure 34: Slide switch S2 schematic.
Figure 35: When slide switch S2 = FX2 PON, signal PS_EN is set to signal FX2_PS_EN driven by the EZ-USB FX2LP USB FX2 microcontroller under user control.
When S2 is turned on (FX2 PON), the 1.2 V and 2.5 V power rails are controlled by the USB (EZ-USB FX2LP USB FX2) microcontroller. At start-up, the USB microcontroller switches off the 1.2 V and 2.5 V power rails and starts up the module in low-power mode. After enumeration, the USB microcontroller firmware switches the 1.2 V and 2.5 V power rails on, if enough current is available from the USB bus.
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S2 position | Default position | Effect on 1.2 V and 2.5 V rails |
---|---|---|
FX2 PON (on) | 1.2 V and 2.5 V rails controlled by USB FX2 microcontroller (signal FX2_PS_EN) PS_EN = FX2_PS_EN = high or low | |
PON (off) | 1.2 V and 2.5 V rails always enabled (PS_EN = high) PS_EN ≠ FX_PS_EN |
Table 14: Slide switch S2 settings overview (1.2 V and 2.5 V rails only).
To command signal FX2_PS_EN, read the reference firmware code.
IOD = 0x03; // Enable PS_EN and disable PROG_B
OED = 0x03; // Configure PS_EN and PROG as outputs
Port D Pin | Alternate Function | Alternate Function is Selected By... | Alternate Function is Described in... |
---|---|---|---|
PD.7:0 | FD[15:8] | IFCFG1 = 1 and any WORDWIIDE bit = 1 | Slave FIFOs chapter 9 on page 99 |
Table from EZ-USB(R) Technical Reference Manual (EZ-USB_TRM.pdf).
Power-rail 3.3V is not controlled by signal PS_EN and is unconditionally enabled.
Figure 38: Power rails 3.3V could not be enabled/disabled by signal PS_EN.
According to the corresponding assembly option, power rail VCCCIO0 can depend or not on the 2.5V power rail.
Figure 37: example of VCCIO0 assembly not dependent on 2.5V power rail. The other way is also possible.
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Figure 35: S2 on position FX2 PON (PS_EN = FX2_PS_EN = high or low ).
Figure 36: Slide switch S2 schematic.
Figure 37: When slide switch S2 = FX2 PON, signal PS_EN is set to signal FX2_PS_EN driven by the EZ-USB FX2LP USB FX2 microcontroller under user control.
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Full power operation ( (PS_EN = high): when slide switch S2 is in the right position (PON = power rails unconditionally on), signal PS_EN is set to power rail 3.3V. Thus power rails 2.5V and 1.2V are unconditionally enabled.
Figure 34: S2 on position PON (PS_EN ≠ FX2_PS_EN = x; PS_EN = high ).
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Power-rail 3.3V is not controlled by signal PS_EN and is unconditionally enabled.
Figure 38: Power rails 3.3V could not be enabled/disabled by signal PS_EN.
According to the corresponding assembly option, power rail VCCCIO0 can depend or not on the 2.5V power rail.
Figure 37: example of VCCIO0 assembly not dependent on 2.5V power rail. The other way is also possible.
Table 14 summarizes all switching options implied by slide switch S2 and firmware signal FX2_PS_EN (under the standard assembly option).
power rail | S2= PON | S2 = FX2 PON and | S2 = FX2 PON and |
---|---|---|---|
1.2V | on | on | off |
2.5V | on | on | off |
VCCCIO0 (= 2.5V) | on | on | off |
VCCCIO0 (= 3.3V) | on | on | on |
(2) R131 soldered / R132 unsoldered
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