1.9.1 Internal Clamp Diode Circuitry

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All I/O banks—MSIO, MSIOD, and DDRIO—have a clamp diode. The PCI 3.3V I/O standard requires a pull-up clamp diode which is available only in MSIO banks. If you use non-PCI I/O standards in MSIO banks, the pull-up diode clamp is disabled and is available for hot-swapping, which requires the pull-up diode clamp to be disabled. You cannot disable the pull-up clamp diode for the MSIOD and DDRIO banks for any I/O standard supported by these banks.

Figure 1-20. Internal Clamp Diode Control Circuitry

The following table lists the I/O banks that have clamp diode.

Table 1-18. I/O Banks with Clamp Diode
I/O Bank	I/O Standard	Clamp Diode
MSIO	PCI	Present
MSIO	All non-PCI standards	Not present
MSIOD	All I/O standards	Present
DDR	All I/O standards	Present

For more information about hot swapping and cold sparing applications, see AC396: SmartFusion2 and IGLOO2 in Hot Swapping and Cold Sparing Application Note.