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.
When S2 is turned on (closed, FX2 PON), the power rails 1.2 V and 2.5 V 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 enables (switches on) power rails 1.2 V and 2.5 V, 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).
S2 position | Default position | Effect on 1.2 V and 2.5 V rails |
---|---|---|
FX2 PON (on, closed) | Power rails 1.2 V and 2.5 V controlled by USB FX2 microcontroller (signal FX2_PS_EN) PS_EN = FX2_PS_EN = 1 or 0 | |
PON (off, open) | Power rails 1.2 V and 2.5 V always enabled (PS_EN = 1) PS_EN ≠ FX_PS_EN = 1 or 0 |
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
Table from EZ-USB(R) Technical Reference Manual (EZ-USB_TRM.pdf)
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 |
Signal PS_EN enables (1) or disables (0) power rails 1.2 V and 2.5 V.
Power-rail 3.3V is not controlled by signal PS_EN and is unconditionally enabled.
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.
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).
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).
Full power operation (PS_EN = 1): 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 1.2 V and 2.5 V are unconditionally enabled.
The table below 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 |
(1) R131 populated / R132 unpopulated
(2) R131 unpopulated / R132 populated
Slide switch S2 can be replaced by one resistors in the following cases:
Assembly option when resistor R17 not populated and R19 populated is equivalent to slide switch S2 permanently set to PON.
Assembly option when resistor R17 populated and R19 not populated is equivalent to slide switch S2 permanently set to FX2 PON.
Any other assembly options of R17 and R19 are not allowed.