"> AR# 20246: Virtex-4 ES - How do I reduce the high current requirement of ICCAUX after configuration?

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AR# 20246

Virtex-4 ES - How do I reduce the high current requirement of ICCAUX after configuration?

Description

The errata for some Virtex-4 FPGAs states that ICCAUX requires 750 mA of current during initial configuration. See the errata document which accompanies your devices to determine whether this issue must be considered.

The errata can be accessed from: http://www.xilinx.com/support/documentation/virtex-4_errata.htm

How do I reduce the current after configuration?

Solution

As stated in the errata, for the following interface only, it is possible to not modify the design to work around this issue with BitGen setting.

For JTAG Configuration Mode

Use the iMPACT or ChipScope Pro tools in ISE design tools to configure these devices.

For Slave Serial Configuration Mode

When generating the bitstream with BitGen, use the following option:

-g EngineeringSample:Serial

For Slave SelectMAP Configuration Mode

When generating the bitstream with BitGen, use the following option:

-g EngineeringSample:SelectMAP8

If configuration interface is Master Serial or Master SelectMAP and you have access to JTAG interface, you can work around this issue by putting the device in read-back mode using the RCFG command in JTAG:

To send the RCFG command, the following instructions must be sent to the device:

FFFFFFFF (PAD DATA)
AA995566 (SYNCH WORD)
30008001 (Write to CMD register)
00000004 (RCFG command)
30008001 (Write to CMD register)
0000000D (DESYNCH command)
00000000 (PAD DATA)
00000000 (PAD DATA)

This will synchronize the device, send in the RCFG command, and then de-synchronize the device.

The above commands can be sent to the device using a SVF file. The SVF file must contain the following:

//Reset TAP controller
TRST OFF;
ENDIR IDLE;
ENDDR IDLE;
STATE RESET IDLE;
//Assume only one device in the JTAG chain
// Loading device with a `cfg_in` instruction.
SIR 10 TDI (3C5) ;
// Loading device with RCFG command
SDR 192 TDI (00000000 00000000 20000000 8001000C 66AA9955 FFFFFFFF) ;

This requirement to put the device in read-back will be removed in future versions of ES silicon, as well as in production devices.

It is possible to reduce the current draw within your design. This work-around will be applicable to any configuration mode since it utilizes ICAP to place the device in read-back mode.

Sample reference design can be downloaded from the following link:
http://www.xilinx.com/txpatches/pub/applications/misc/vccaux.zip

AR# 20246
Date Created 09/03/2007
Last Updated 12/15/2012
Status Active
Type General Article
Devices
  • Virtex-4