Determining Dynamic Memory Latency Impact on Low Power Mesh Re Keying Operations
Dynamic memory access delays during mesh key rotation increase microcontroller active time, causing battery voltage droop and lost frame acknowledgments.
SRAM Wait States
Meaning
Clock cycles added during memory access operations align the speed of the processor with the response time of volatile storage. Configuring sram wait states prevents data corruption that occurs when a high-speed core tries to read data before the memory lines have stabilized. This register configuration is set during the early stages of boot initialization.
Memory Access
Read operations require the memory cells to assert the requested data on the bus within a fraction of a clock cycle. When the processor clock speed exceeds the access speed of the memory, adding sram wait states gives the physical lines the time needed to reach valid logic levels. This margin avoids read errors during high-frequency bursts, which would otherwise trigger hard faults or memory corruption.
The timing register values are determined during the board brings-up phase.
Clock Sync
System clocks must be scaled to match the temperature and voltage variations of the board. An increase in operating temperature slows down the memory transistors, requiring additional sram wait states to maintain stability. Hardware designers test this timing margin across the entire specified temperature range of the product.
Throughput Penalty
Each added delay cycle reduces the overall execution speed of the firmware. Minimizing sram wait states is achieved by optimizing the memory bus frequency or running code directly from high-speed cache. This balancing act allows the processor to run at maximum efficiency without risking system crashes.