OMAP-L132/L138引导加载器使用指南

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"这份应用报告详细介绍了OMAP-L132/L138处理器的引导加载程序（Bootloader）功能，包括各种启动机制、AIS（Application Image Script）启动过程、生成引导脚本的工具AISgen、从外部主设备启动的协议、以及UART Boot Host GUI，用于从主机PC引导设备。报告还涵盖了启动需求、约束和默认设置，并提供了一些附录，如启动模式选择表。" 在深入探讨之前，我们首先理解一下OMAP-L132/L138 Bootloader的基本概念。OMAP-L132/L138是德州仪器（TI）开发的微控制器，它们集成了ARM7TDMI-S CPU核心和C674x DSP核心，广泛应用于嵌入式系统设计。Bootloader是系统启动时运行的第一段代码，负责初始化硬件、加载操作系统内核或应用程序到内存中。 1. **启动模式** (Boot Modes): OMAP-L132/L138支持多种启动模式，包括非AIS（Application Image Script）模式。这些模式允许开发者根据具体应用场景选择合适的启动方式。 2. **非AIS启动模式** (Non-AIS Boot Modes): 在这些模式下，Bootloader不依赖于AIS脚本来执行启动流程。可能包括从内部存储器、外部存储器或者特定的硬件引脚状态启动。 3. **AIS启动** (AIS Boot): AIS是一种定制化的启动流程，它允许用户通过脚本定义启动序列，包括加载多个映像、设置CPU寄存器、配置系统参数等。AIS增强了灵活性，适应了复杂系统的启动需求。 4. **AISgen工具** (AISgen): 这是一个用于生成AIS引导脚本的工具，帮助开发者自定义启动过程，生成符合特定需求的二进制脚本。 5. **主设备启动** (Master Boot): 当OMAP-L132/L138作为主设备时，可以从连接的从设备（如SPI、I2C或EVM上的闪存）中启动。这涉及特定的通信协议来传输启动数据。 6. **从外部主设备启动** (Slave Boot): 在这种模式下，OMAP-L132/L138作为从设备，由外部主机（例如PC）通过UART（通用异步接收发送器）接口引导启动。 7. **UART Boot Host** (UART Boot Host): 提供了一个UART Boot Host GUI，使得用户可以利用个人电脑作为UART Boot主设备，方便地对OMAP-L132/L138进行调试和更新。 8. **启动要求、约束与默认设置** (Boot Requirements, Constraints and Default Settings): 报告中详细列出了引导过程中可能遇到的限制、默认设置以及Bootloader的假设，这对于理解和优化启动流程至关重要。 9. **参考文献** (References): 为深入学习和进一步研究提供了相关资料链接。 10. **附录** (Appendices): 包括启动模式选择表等实用信息，帮助开发者快速识别和选择适当的启动模式。这份应用报告不仅提供了理论知识，还通过实际工具和示例，使得开发者能够更好地掌握OMAP-L132/L138 Bootloader的使用，从而有效地开发和调试基于这些处理器的系统。

0x58535902

CRC

Seek

0x58535902

CRC

Seek

EnableCRC

SectionLoad

Error

OPCODE_SYNC

CRC

DeviceHost

0x58535908

Application Image Script (AIS) Boot

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4.5 Validate CRC Command (0x58535902)

This command is used to validate the CRC calculated by the bootloader.

Figure 10. Validate CRC Command

This command takes two arguments: the CRC and the seek value. The CRC is the expected value of the

CRC with which the calculated CRC should be compared. In the case of a CRC match, the seek value is

ignored and the next command is executed. However, in the case of a CRC mismatch, the seek value can

be added to the current position in AIS to locate the last Section Load/Section Fill command so that the

command can be executed again.

Figure 11. Handling CRC Error

This command behaves differently for master- and slave-boot modes. In master-boot mode, the

bootloader reads the expected CRC from the boot device and compares it with the calculated CRC. In

case of an error, the bootloader adds the seek value to the current read position in AIS and starts

executing commands from that position in AIS.

Figure 12. Validate CRC Flow for Slave Mode

In slave-boot mode, on receiving the Validate CRC command, the bootloader provides the calculated CRC

to the host. The host then compares this value with the one from AIS and updates its AIS read position,

depending on the result of the CRC comparison. In the case of an error, the host sends the Start-Over

command to the device so that the bootloader can re-initialize the calculated CRC and be ready to receive

the next command.

Figure 13. Start-Over Command

The Start-Over command (0x58535908) takes no arguments or data. This command does not appear in

AIS and is only used in slave-boot mode by the host to recover from a CRC error.

Using the OMAP-L132/L138 Bootloader SPRAB41D– August 2011

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0x58535906

Address

0x58535905

Address

0x58535963

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Application Image Script (AIS) Boot

4.6 Jump & Close Command (0x58535906)

The Jump & Close command is used to mark the end of AIS. On receiving this command, the bootloader

closes the boot peripheral, restores the selected configurations of the device to its default state, and then

transfers control to the user application.

Figure 14. Jump and Close Command

This command takes one argument: the entry point of the ARM application. This is the address the

bootloader transfers control to after closing the boot peripheral. The application starts execution after this

jump and the bootloader loses its control over the device.

4.7 Jump Command (0x58535905)

This command is similar to the Jump & Close command, except that the bootloader does not close the

boot peripheral and does not change any device state. This command is not used to transfer control to the

application. Rather, it is used to execute a temporary code, which may tweak the bootloader or device

state. This command is used to add post-ROM features to the bootloader.

Figure 15. Jump Command

This command takes one argument: the address of a temporary function to be called. This function should

be loaded to the device memory before the Jump command, and it should also return control to the

bootloader after performing its intended task.

4.8 Sequential Read Enable Command (0x58535963)

When booting from a serial peripheral interface (SPI) or inter-integrated circuit (I2C) slave device, the

bootloader uses a random read method to read the boot image from the slave memory device. This

method requires sending a read command and a read address to read each byte. Many recent memory

devices support reading in sequential method, where data can be read in sequential order without sending

a read command/address for each byte. Using this method to read data greatly reduces boot time. The

Sequential Read Enable command is used to enable the bootloader to use the sequential read method.

Figure 16. Sequential Read Enable Command

This command takes no arguments or data.

4.9 Function Execute Command (0x5853590D)

The Function Execute command is a generic interface for device-specific initialization functions such as

phase-locked loop (PLL) and external memory interface (EMIF) configuration. A set of pre-defined

functions are part of the ROM and a function table is maintained by the bootloader with pointers to each of

them. The Function Execute command can be used to execute any of them. Details of pre-defined ROM

functions that can be called using this command are given in Appendix D.

SPRAB41D– August 2011 Using the OMAP-L132/L138 Bootloader

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