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Scroll pdf title
titleDip switch S1[A:D aka 1:4]. The switch S1B is the one with label 2 and B

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Scroll pdf title
titleWhen Dip switch S1B = 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 S1B is turned off  (open) (FX2 PON position), the 1.2 V, 1.5 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 power rails 1.2 V, 1.5 V and 2.5 V and starts up the module in low-power mode. After enumeration, the USB microcontroller firmware enables (switches on) the power rails 1.2 V, 1.5 V and 2.5 V, if enough current is available from the USB bus.

When S1B is turned on (closed) (PON position), the power rails 1.2 V, 1.5 V and 2.5 V are always enabled (switched on).

Scroll pdf title
titleDip switch S1B settings overview (power rails 1.2 V, 1.5V and 2.5 V only).

S1B position

Default position

Effect on 1.2 V, 1.5 V and 2.5 V rails

FX2 PON (off, open) 

(tick)

Power rails 1.2 V, 1.5 V and 2.5 V controlled by USB FX2 microcontroller (signal FX2_PS_EN)

PS_EN = FX2_PS_EN = 1 or 0

PON (on, closed)

(error)

Power rails 1.2 V, 1.5 V and 2.5 V always enabled (PS_EN = 1)

PS_ENFX_PS_EN = 1 or 0


Signal FX2_PS_EN

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

 

Scroll pdf title
titleTable from EZ-USB(R) Technical Reference Manual (EZ-USB_TRM.pdf).

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

  • Signal PS_EN enables (1) or disables (0) power rails 1.2 V, 1.5 V and 2.5 V.

    Scroll pdf title
    titlePower rails 1.2 V, 1.5 V and 2.5 V could be enabled/disabled by signal PS_EN.


  • Power-rail 3.3V is not controlled by signal PS_EN and is unconditionally enabled. 

    Scroll pdf title
    titlePower rails 3.3V could not be enabled/disabled by signal PS_EN.

     

VCCIO assembly options

 
Info
According to the corresponding assembly option, power rail VCCCIO0
can
(enabled by PS_EN and switch S1B ) can depend or not on the power rail 2.5V.

VCCIO0 voltage can be configured in 3 ways:

  • 2.5V - When resistor R103 is populated and resistor R102 is not populated.
  • 3.3V - When R103 is not populated and resistor R102 is populated.
  • 1.2 V ÷ 3.3 V (External supply) - When R103 is not populated and R102 is not populated. In this case external supply source have to be connected to pins 1, 2, 3, 4 of J4 B2B connector(1).

 (1) See Spartan-6 documentation fo VCCIO power range.

Scroll pdf title
titleExample of VCCIO0 assembly not dependent on 2.5V power rail. The other way is also possible.

 

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Scroll pdf title
titleDip switch S1B settings overview ( 1.2 V, 1.5 V , 2.5 V, VCCIO0).

power rail

S1B= PON
(PS_EN = 1)

(PS_EN ≠ FX2_PS_EN)
(Full power)

S1B = FX2 PON and
PS_EN = FX2_PS_EN = 1

(Dynamic full power)

S1B = FX2 PON and
PS_EN = FX2_PS_EN = 0

(Dynamic low power)

1.2 V

on

on

off

1.5 Vononoff

2.5 V

on

on

off

VCCCIO0 (= 2.5 V)
R102-R103+ assembly (1)

on

on

off

VCCCIO0 (= 3.3 V)
R102+R103- assembly (2)

on

on

on

(1) R102 unpopulated / R103 populated

(2) R102 populated / R103 unpopulated