Customer Update

Readback Specification Established on XC4000/D/E

Xilinx is now officially establishing the readback specification of the XC4000, XC4000D and XC4000E to be 1MHz-2MHz. The performance level for the readback feature has never been officially specified, although it had been described in a published application note to be 10KHz-1MHz (

XAPP 015.000 "Using the XC4000 Readback Capability"). Establishing this specification improves performance of the device and allows a higher performance of this powerful feature. Xilinx believes that establishing this specification will adversely affect very few users. However, for those that are affected, Xilinx can provide silicon that meets 10KHz-1MHz operation. Contact your Xilinx sales representative for more information.

Also, this change will require a software patch to the X-Checker accessory, which will adjust its operating frequency to meet the new specification. This patch is now on the Xilinx BBS (PC only) and FTP site. Versions are available for the PC, Sun workstation, and HP workstation. The existing X-Checker operation can be used, however a small chance exists that the current X-Checker may register erroneous readback errors. If readback errors are encountered, they are most likely indicative of X-Checker operating outside of the specification range, and not a reflection of the configuration data integrity. If you encounter a readback issue, please contact your Xilinx sales representative or the Xilinx hotline.

Updated specifications have been added to the XC4000 Series Data sheet. Trch and Trcl are the key parameters affected. This affects only the XC4000 (including the "D") and XC4000E families, and not the XC4000A, XC4000H, XC4000EX or any other Xilinx product families.

9/15/96 XCU 099601