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# CalmRISC/CalmRISC16 Samsung CalmRISC16 Core Evaluation Board

## Overview

The Samsung CalmRISC16 evaluation platform consists of two boards connected by a ribbon cable. One board contains the CPU core and memory. The other board is called the MDSChip board and provides the host interface. The calmRISC16 is a harvard architecture with separate 22-bit program and data addresses. The instruction set provides no instruction for writing to program memory. The MDSChip board firmware (called CalmBreaker) provides a pseudo register interface so that code running on the core has access to a serial channel and a mechanism to write to program memory. The serial channel is fixed at 57600-8-N-1 by the firmware. The CalmBreaker firmware also provides a serial protocol which allows a host to download a program and to start or stop the core board.

The following RedBoot configurations are supported:

Configuration | Mode | Description | File
--- | --- | --- | ---
ROM | [ROM] | RedBoot running via the MDSChip board. | redboot_ROM.ecm

## Initial Installation Method

The CalmRISC16 core is controlled through the MDSChip board. There is no non-volatile storage available for RedBoot, so RedBoot must be downloaded to the board on every power cycle. A small utility program is used to download S-record files to the eval board. Sources and build instructions for this utility are located in the RedBoot sources in: `packages/hal/calmrisc16/ceb/current/support`

To download the RedBoot image, first press the reset button on the MDSChip board. The green 'Run' LED on the core board should go off. Now, use the utility to download the RedBoot image with:

    $ calmbreaker -p /dev/term/b --reset --srec-code -f redboot.elf

Note that the '-p /dev/term/b' specifies the serial port to use and will vary from system to system. The download will take about two minutes. After it finishes, start RedBoot with:

    $ calmbreaker -p /dev/term/b --run

The 'Run' LED on the core board should be on. Connecting to the MDSboard with a terminal and typing enter should result in RedBoot reprinting the command prompt.

## Special RedBoot Commands

None.

## Special Note on Serial Channel

The MDSChip board uses a relatively slow microcontroller to provide the pseudo-register interface to the core board. This pseudo-register interface provides access to the serial channel and write access to program memory. Those interfaces are slow and the serial channel is easily overrun by a fast host. For this reason, GDB must be told to limit the size of code download packets to avoid serial overrun. This is done with the following GDB command:

    (gdb) set download-write-size 25

## Rebuilding RedBoot

These shell variables provide the platform-specific information needed for building RedBoot according to the procedure described in Chapter 3:

    export TARGET=calm16_ceb
    export ARCH_DIR=calmrisc16
    export PLATFORM_DIR=ceb

The names of configuration files are listed above with the description of the associated modes.

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