AMBA Specification (Rev 2.0)简介

一、配置时钟时，经常看到APB、AHB，一直也没仔细关注过，抽空先粗略了解一下。

二、AMBA Specification (Rev 2.0)定义了三个总线，分别是AHB、ASB和APB。
1、AHB：Advanced High-performance Bus。
AHB is a new generation of AMBA bus which is intended to address the requirements of high-performance synthesizable designs. AMBA AHB is a new level of bus which sits above the APB and implements the features required for high-performance, high clock frequency systems including:
• burst transfers
• split transactions
• single cycle bus master handover
• single clock edge operation
• non-tristate implementation
• wider data bus configurations (64/128 bits).

2、ASB：Advanced System Bus。
The Advanced System Bus (ASB) specification defines a high-performance bus that can be used in the design of high performance 16 and 32-bit embedded microcontrollers.
AMBA ASB supports the efficient connection of processors, on-chip memories and off-chip external memory interfaces with low-power peripheral macrocell functions.The bus also provides the test infrastructure for modular macrocell test and diagnostic access.

3、APB：Advanced Peripheral Bus。
The Advanced Peripheral Bus (APB) is part of the Advanced Microcontroller Bus Architecture (AMBA) hierarchy of buses and is optimized for minimal power consumption and reduced interface complexity.
The AMBA APB should be used to interface to any peripherals which are low-bandwidth and do not require the high performance of a pipelined bus interface.
The latest revision of the APB ensures that all signal transitions are only related to the rising edge of the clock. This improvement means the APB peripherals can be integrated easily into any design flow, with the following advantages:
• performance is improved at high-frequency operation
• performance is independent of the mark-space ratio of the clock
• static timing analysis is simplified by the use of a single clock edge
• no special considerations are required for automatic test insertion
• many Application-Specific Integrated Circuit (ASIC) libraries have a better selection of rising edge registers
• easy integration with cycle based simulators.
These changes to the APB also make it simpler to interface it to the new Advanced
High-performance Bus (AHB).