AXI4 / AXI4-Lite / AXI-Stream (AMBA)

ON-CHIP BUS PROTOCOLS

The ARM AMBA AXI protocol family is the dominant on-chip interconnect standard. SSN engineers verify AXI interfaces with precision:

Five-channel handshake coverage: AR, AW, R, W, B channels — including backpressure, out-of-order responses, and ID ordering rules.

AXI4 burst types: FIXED, INCR, WRAP — boundary alignment, 4K address boundary crossing detection.

Atomic operations: exclusive access (EXOKAY), locked access sequences.

AXI Quality of Service (QoS) arbitration and bandwidth throttling scenarios.

AXI-Stream TKEEP/TLAST/TUSER sideband signal protocol checking.

Protocol assertions aligned to AMBA AXI and ACE Protocol Specification IHI0022.

APB (Advanced Peripheral Bus)

APB is the AMBA low-power, low-complexity bus used for peripheral register access. SSN verification of APB includes:

SETUP and ACCESS phase timing verification, PREADY wait-state insertion, and PSLVERR error response checking.
APB bridge behavior: AXI-to-APB and AHB-to-APB bridge protocol conversion.
Register-level access via UVM RAL over APB front-door paths.
Bus contention and arbitration corner cases in multi-master APB configurations.

AHB (Advanced High-performance Bus)

AHB sits between AXI and APB in the AMBA hierarchy. SSN verifies AHB pipelining, split transactions, retry responses, multi-layer AHB interconnects, and the AHB-Lite subset widely used in Cortex-M-based SOCs.

CPRI / eCPRI

Common Public Radio Interface (CPRI) and enhanced CPRI (eCPRI) are the fronthaul protocols connecting baseband units to remote radio heads in 4G and 5G infrastructure. SSN has verified CPRI controllers in multiple 5G baseband ASIC projects, covering hyperframe synchronization, I/Q data mapping, vendor-specific region handling, and link bring-up state machines.