Multi-frequency clock skew control for inter-chip communication in synchronous digital systems

Abstract

Embodiments are disclosed of an apparatus capable of performing multi-rate synchronous communication between component chips. Each chip may receive a common clock reference signal, and may generate an internal clock signal dependent on the clock reference signal. A clock distribution tree and phase-locked loop may be used to minimize internal clock skew at I/O circuitry at the chip perimeter. Each chip may also generate an internal synchronizing signal that is phase-aligned to the received clock reference signal. Each chip may use its respective synchronizing signal to synchronize multiple clock dividers that provide software-selectable adjusted-frequency clock signals to the I/O cells of the chip. In this way, the adjusted-frequency clock signals of the multiple chips are edge-aligned to the low-skew internal clock signals, and phase-aligned to the common clock reference signal, allowing the I/O cells of the multiple chips to perform synchronous communication at multiple rates with low clock skew.