Debug interface including operating system access of a serial/parallel debug port

Abstract

A debug interface supports data transfer using read and write system calls that communicate data without stopping an executing kernel. The printf( ) command passes an information string to an executing operating system. The information string summons the operating system to use a serial debug port to signal to a debug device, such as a host system, that is connected to the serial port. The debug interface-supported read and write operations and system calls allow the kernel and executing applications software, respectively, to continue executing during the read and write data transfers. The debug interface includes support for a plurality of extended function sideband signals that extend the functionality of the read and write functionality to allow the processor to concurrently run kernel and application programs while transferring data using read and write operation. The extended function sideband signals include a command acknowledge signal (CMDACK), a dual-purpose break execution and trace control signal (BRTC), an execution stopped and receive data signal (STOPTX), and an off-chip trigger event signal (TRIG). The debug interface further includes a buffer for transferred data The kernel may run a first data transfer command which is not fully transmitted when a second data transfer command is issued. The operating system supports buffering of the data evoked by the second data transfer command using a conventional queuing operation.

Dependencies are inferred from the claim text.