Shared bus in-circuit emulator system and method

Abstract

An in-circuit emulator, alternatively referred to as a microcontroller debugging system, has a control processor having I/O ports and a multiplexed address/data bus port, an emulation processor having I/O ports and a multiplexed address/data bus port, an emulation memory having address inputs, a data bus interface and a plurality of two-to-one multiplexers. The in-circuit emulator is configured such that the control processor and the emulation processor each have at least one port directly coupled to the data bus of the emulation memory without the use of external tri-state buffers, this is referred to as the shared bus. An address latch, shared by both processors, has its inputs coupled to the shared bus. The outputs of the address latch form a portion of the emulation memory address input, and are coupled to a corresponding portion of the emulation memory address inputs. The emulation processor is supplied with a clock which is selected from the group consisting of: the same clock input signal used by the control processor, a clock synchronized with the internal clock of the control processor and a clock which is asynchronous with respect to the internal clock of the control processor.