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AR# 25058

11.4 Spartan-3A MAP - How to debug "ERROR:Pack:1107 - Unable to combine the following symbols into a single IOB"


My design is failing during MAP with the following PACK error message:

"ERROR:Pack:1107 - Pack was unable to combine the symbols listed below into a single IOB component because the site type selected is not compatible. Theroot cause of failure is that the IOSTANDARD=PCI33_3 property requires abi-directional capable IO site and is not supported in input-only IO sites.

Further explanation:
The component type is determined by the types of logic and the properties and configuration of the logic it contains. In this case an IO component of typeIOB was chosen because the IO contains symbols and/or properties consistentwith PCI bypass usage and a IOSTANDARD=PCI33_3 property. Please double checkthat the types of logic elements and all of their relevant properties andconfiguration options are compatible with the physical site type of theconstraint.

Symbols involved:
BUF symbol "XLXN_3_IBUF" (Output Signal = XLXN_3_IBUF)
PAD symbol "XLXN_3" (Pad Signal = XLXN_3)
Component type involved: IOB
Site Location involved: N6
Site Type involved: DIFFMI_NDT"

The message seems to indicate that a PAD and BUF symbol cannot be combined into an IOB component. Can this be the case?


This valid error messagehas the difficult task of trying to describe a wide variety of conflicts between site types and the logical instances constrained to them. The key elements for this specific error are as follows:

  • The site type involved (N6 in a xc3s1400a-fg484-4) is an IP_L31P_3 pin, which is an "input-only" pin.
  • The component that is being constructed is an IOB (rather than an IBUF) and cannot be placed in the input-only site.
  • Less obvious is that the I/O Standard, PCI33_3, led to the creation of an IOB component even though only the input side was used; PCI33_3 is not supported by input-only sites because of a hardware limitation (no PCI clamp diodes).

Beginning with ISE Design Suite 11.1, the "Pack:1107" message has been modified to describemore explicity why the pack failed. There are three sections to the message:

  • The first section attempts to describe why the error occurred. In this cases it says, "The root cause of failure is that the IOSTANDARD=PCI33_3 property requires a bi-directional capable IO site and is not supported in input-only IO sites".
  • The second section attempts to explain why the component type was chosen.
  • The third section summarizes the issue by listing the symbols involved, the component type that resulted, the site involved, and the site type.

NOTE:If your case involves a similar error for a different component type, you can still use this Answer Record as a template for investigating your particular issue. You should focus on the component type that is being created and the site type to which it is constrained (e.g., why is the particular component type being created by MAP and why is the intended site location not suitable?).

AR# 25058
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article
  • Spartan-3A
  • ISE Design Suite - 11.4