TE0320 is provided with a slide switch S2.
Slide switch S2 conditions the value of signal PS_EN.
In this way, S2 conditionally/unconditionally enables the 1.2 V and 2.5 V power rails.
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Figure 33: Slide switch S2 (angle view).When S2 is turned on (closed, FX2 PON), the power rails 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 1enables (switches on) power rails 1.2 V and 2.5 V power rails on, if enough current is available from the USB bus.
When S2 is turned off (open, PON), the 1.2 V and 2.5 V power rails are always enabled (switched on).
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When S2 is turned on (FX2 PON), make sure that no signals are applied to the input pins when power-rails are disabled by the USB microcontroller (at start-up). |
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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
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Table from EZ-USB(R) Technical Reference Manual (EZ-USB_TRM.pdf)
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Signal PS_EN enables (1) or disables (0) power rails 1.2 V and 2.5 V.
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Power-rail 3.3V is not controlled by signal PS_EN and is unconditionally enabled.
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According to the corresponding assembly option, power rail VCCCIO0 can depend or not on the power rail 2.5V.
Voltage VccIO for bank B0 shall span from 2.5 V to 3.3 V. VccIO can be supplied either externally or internally to the micromodule.
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Spartan-3 I/Os are not 5 V tolerant. Applying more than the recommended operating voltages at any pin, results in a damaged FPGA (see Xilinx Answer AR#19146). |
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When slide switch S2 is in the left position ( = FX2 PON : power rails conditionally on depending on signal FX2_PS_EN), signal PS_EN is set to signal FX2_PS_EN (PS_EN = FX2_PS_EN) driven by the EZ-USB FX2LP USB FX2 microcontroller under user control (IOD and OED of fw.c).
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Full power operation ( (PS_EN = high1): 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 rails 1.2 .5V V and 12.2V 5 V are unconditionally enabled.
Figure 34:
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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.
The table below
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).
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1) R131 |
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populated / R132 |
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unpopulated ( |
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2) R131 |
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unpopulated / R132 |
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Table 14: Slide switch S2 settings overview ( 1.2V , 2.5V, VCCIO0).
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Slide switch S2 can be replaced by one resistors in the following cases:
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Assembly option when resistor R17 not populated and R19 populated is equivalent to slide switch S2 permanently set to PON.
Figure 37: assembly
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Assembly option when resistor R17 populated and R19 not populated is equivalent to slide switch S2 permanently set to FX2 PON.Figure 38:
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Any other assembly options of R17 and R19 are not allowed. |
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