Slave Device Clock Generation via Reserved SPI Cycles
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Solution Overview
Problem
Existing serial communication systems, such as SPI, face complexity in providing a robust clock to slave devices for performing logical operations, often requiring local clock generators that can be costly, complex, and asynchronous to the serial clock.
Innovation Solution
The introduction of reserved clock cycles in the serial data word transfer allows the slave device to generate a derived clock based on the serial clock pulses, eliminating the need for a local clock generator and ensuring synchronous operations with the master device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a local clock generator is provided in the slave device, then robust clock control for logical operations is achieved, but device complexity and cost increase
Solution Approach 1:
The clock generation function is extracted from the slave device and relocated to the master device. The master device now provides not only data but also clock signals through the serial interface, eliminating the need for a separate local clock generator in the slave device. This reduces slave device complexity while maintaining reliable clock control for logical operations.
Solution Approach 2:
The clock signal and data transmission functions are merged into a single serial interface communication channel. The master device combines data output and clock signal generation into one integrated communication path, allowing the slave device to receive both data and timing information through the same interface, thereby reducing overall system complexity.
2Reliability
If a local clock generator is used in the slave device, then clock control is achieved, but noise disturbances increase
Solution Approach 1:
The local clock generator, which is a potential noise source, is extracted and removed from the slave device. By obtaining clock signals from the master device through the serial interface instead of generating them locally, the slave device eliminates the noise disturbances associated with local clock generation while maintaining precise control of logical operations.
3Reliability
If reserved clock cycles are introduced in serial data word transfer, then synchronous operation is achieved, but communication protocol complexity increases
Solution Approach 1:
The communication protocol incorporates periodic reserved clock cycles within the serial data word transfer sequence. These regularly spaced reserved cycles provide explicit timing reference points that enable the slave device to synchronize its logical operations with the master device, achieving reliable synchronous operation through structured periodic timing signals.
Solution Approach 2:
Reserved clock cycles act as intermediary timing signals embedded within the data transmission stream. These intermediate clock pulses serve as reference markers that mediate between the data communication function and the synchronous operation requirement, allowing the slave device to derive accurate timing information without requiring a separate clock connection.
Data Source
AI summary
Versatility and flexibility of integrated circuits can be accomplished by remote control via a serial interface (102,122), such as SPI. Read/write accesses to the SPI slave (120) node can be achieved according to SPI protocol by the master node (100). Additionally, a state machine associated to the slave node SPI needs a local clock to exercise the control of the analog functions following a write access. The serial protocol defines a serial data word transfer to comprise a number of reserved clock cycles that are not assigned for communicating a data bit value of the data word. The slave device comprises a clock unit (124) coupled to the serial clock line for providing a derived clock (125) based on reserved clock cycles. The derived clock is used internally in the slave device to perform internal synchronous operations.