DEFENSIVE PUBLICATION: COHERENT READ OF MULTI-WORD DATA FROM TPU CAMSHAFT DECODER FUNCTION
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2002-Aug-07
The "Coherent Read of Multi-word data from TPU Camshaft Decoder Function" (hereafter referred to as the INVENTION) solves a problem in a system that uses dual ported RAM. In this partic- ular system, the dual ported RAM is on-chip and is used to exchange data between a CPU and the microengine of one of the on-chip peripherals, the Time Processor Unit (TPU). The dual ported RAM guarantees one long-word (two words) of uninter- rupted access. This means that the CPU can read two adjacent words of data and be ensured that the read is coherent, that is, the TPU cannot update one of the words in the middle of the read. The same is true for the TPU. However, in this particular sys- tem, there is no mechanism to handle coherent data reads when the data is longer than two words. This presents a problem in applications in which it is nec- essary to exchange data longer than two words in length. Because the RAM, CPU, and TPU all reside on the same microcontroller (MCU), no hardware mechanism can be implemented by the user to solve this problem; the hardware constraints are already defined. Thus, a software solution must be implemented.