Global Timebase Distribution Using Gray Code Encoding
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Solution Overview
Problem
Existing methods for distributing a global clock signal in system-on-chip devices face significant jitter and latency issues due to the use of binary timebase distribution over data buses, leading to inaccuracies in clock synchronization among multiple modules operating at different clock rates.
Innovation Solution
A global timebase system that broadcasts a Gray-coded count value over a global timebase bus, utilizing a binary counter and binary-to-Gray-code converter for accurate synchronization, with each receiver module converting back to binary form and extending local timebases using a local counter, thereby minimizing jitter and latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If binary timebase distribution is used over data buses, then the system can operate with standard binary encoding, but significant jitter and latency occur leading to synchronization inaccuracies
Solution Approach 1:
The patent changes the encoding parameter from binary to Gray code for timebase distribution. This parameter change ensures that only one bit changes between consecutive count values, eliminating multi-bit transitions that cause jitter and latency in binary encoding, thereby improving synchronization accuracy and reducing timing errors.
Solution Approach 2:
The patent introduces Gray code as an intermediary encoding scheme between the binary counter and the distribution bus. This intermediary representation acts as a mediator that preserves the sequential counting function while eliminating the harmful multi-bit simultaneous transitions of binary code, thus reducing jitter without requiring fundamental changes to the counter architecture.
2Measurement precision
If binary timebase count values are distributed over the bus, then the distribution system is simple, but the synchronization accuracy degrades due to multiple bits changing simultaneously
Solution Approach 1:
The patent changes the encoding parameter from binary to Gray code for timebase distribution. This parameter change ensures that only one bit changes between consecutive count values, eliminating multi-bit transitions that cause jitter and latency in binary encoding, thereby improving synchronization accuracy and reducing timing errors.
3Adaptability or versatility
If the counter width is increased to accommodate faster clock domains, then the synchronization range improves, but the bus width and distribution complexity increase
Solution Approach 1:
The patent changes the encoding parameter from binary to Gray code for timebase distribution. This parameter change ensures that only one bit changes between consecutive count values, eliminating multi-bit transitions that cause jitter and latency in binary encoding, thereby improving synchronization accuracy and reducing timing errors.
Data Source
AI summary
A global timebase system and method for a system-on-chip synchronizes multiple clock domains in each of a plurality of receiver modules by broadcasting a global timebase count value as Gray code over a global timebase bus. A global timebase generator includes a binary counter and a binary-to-Gray-code converter. Each receiver module registers the global timebase count value with its own local clock and includes a Gray-code-to-binary converter. The converted value, in binary form, may be used as least significant bits of a globally synchronized local timebase. Most significant bits may be generated by a local binary counter incremented at each 1-to-0 transition of the most significant bit of the global timebase count value.