The possible clock sources for the MMCM include:
- IBUF – Global clock input buffer. The MMCM compensates the delay of this path. IBUF represents a global clock pin in the same region. The IBUF must be located at a global clock pin location.
- BUFGCTRL – Internal global clock buffer. The MMCM does not compensate the delay of this path.
- BUFGCE – Global clock buffer. The MMCM does not compensate the delay of this path.