STAMP - The Software Architecture

		Introduction Here is the structure of the firmware I have written. The complete software is written in C-language. And is divided into different modules which represent a higher or lower abstraction level. Main parts of the code is my own code. The ATA/IDE-code I took from other pojects/persons, but found out that this code has not that optimum to run with this processor, so I wrote this codefragment totally new. I hope the following figures are interesting for you. If you have question belonging to a detailled PEC- or INT-dataflow, please eMail me and I will publish more information on this site.

Introduction

Here is the structure of the firmware I have written. The complete software is written in C-language. And is divided into different modules which represent a higher or lower abstraction level. Main parts of the code is my own code. The ATA/IDE-code I took from other pojects/persons, but found out that this code has not that optimum to run with this processor, so I wrote this codefragment totally new.
I hope the following figures are interesting for you. If you have question belonging to a detailled PEC- or INT-dataflow, please eMail me and I will publish more information on this site.

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Block Diagram

The picture below shows the block diagram of the SW-architecture and abstraction layers between high-level and HW-based modules. The main MP3 dataflow is done by two PEC-transfers (see purple arrows).
The red arrows of each module show you, which modul can cause an interrupt. If such an interrupt appears, the endless loop of the MMI-modul registers that and reacts with the corresponding action.

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Memory Organization

This is next interesting point, because the 80c16x supports special access to its internal registers. This access is done with an ordinary memory read/write operation. So the registers are memory mapped and hide some Flash-ROM or RAM-areas, which you can't use any more.
Furthermore, all external devices are attached via chip select-lines and are memory mapped into the full adressregion of the 80c16x.
The next figure shows you how the memory-organization is held in the STAMP-project, and which parts are based on external devices.
Regarding to PEC-transfers: The PEC-transfers work only within the 1st 64 KB block. I solved this restriction with the following memory-organization:

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PEC-Transfers and Interrupt-Handling

I have implemented a lot of interrupt routines and PEC-transfers. It is possible to avoid them, but there are a lot of advantages.
A PEC-transfer is nearly the same than a DMA-transfer of the common CPU-systems. The most difference is, that each byte- or word-transfer should be initiated by a "hidden interrupt". But the transfer of the byte/word will be done without fetching new opcode from flash. Even if the belonging interrupt appears the opcode for that transfer-operation is injected into the prefetch-pipeline of the CPU. So no special time to fetch new code, and clearing of the pipeline is necessary. This important behaviour of the CPU makes these PEC-transfers so fast. The so called "hidden interrupt" also does not need a interrupt service routine, because the action for that interrupt is the PEC-transfer.
The interrupt-sources to initiate the transfer from IDE to RAM-buffer is done by a timer and the transfer from that buffer to the Decoder-IC is initiated by a SSC-Interrupt every time the SSC-output-buffer runs empty.

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Tool Chain

I am using an older version of the Tasking C166 compiler. An alternativ is the compiler from Keil, but I have never used a compiler from them. The Tasking compiler is in the first step very crude but it's working and supports all professional functionality.
Both compiler-versions are available for free via download at the companies internet pages (see my link-page). They have some limits, but for the first project they should work.

On the other hand I am using a very old multi- or voltmeter. One time I have lend out an Osscilloscope, but thats all.

The PCB-design was done with an older Protel -version. I have had some experience with that. But the Eagle-versions are also very useful, because for this PCB-size the SW is for free and is very common.