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3.4 Boot Sequence

3.4.1

Boot Modes

TMS320C6421

Fixed-Point Digital Signal Processor

SPRS346B – JANUARY 2007 – REVISED APRIL 2007

The boot sequence is a process by which the device's memory is loaded with program and data sections,

and by which some of the device's internal registers are programmed with predetermined values. The boot

sequence is started automatically after each device-level global reset. For more details on device-level

global resets, see Section 6.5, Reset.

There are several methods by which the memory and register initialization can take place. Each of these

methods is referred to as a boot mode. The boot mode to be used is selected at reset. For more

information on the bootmode selections, see Section 3.4.1, Boot Modes.

The device is booted through multiple means—primary bootloaders within internal ROM or EMIFA, and

secondary user bootloaders from peripherals or external memories. Boot modes, pin configurations, and

The C6421 boot modes are determined by these device boot and configuration pins. For information on

how these pins are sampled at device reset, see Section 6.5.1.2, Latching Boot and Configuration Pins.

• BOOTMODE[3:0]

• FASTBOOT

• PLLMS[2:0]

BOOTMODE[3:0] determines the type of boot (e.g., I2C Boot, EMIFA Boot, or HPI Boot, etc.). FASTBOOT

determines if the PLL is enabled during boot to speed up the boot process.

PLLMS[2:0] is used by bootloader code to determine the PLL multiplier used during fastboot modes

(FASTBOOT = 1).

The C6421 boot modes are grouped into two categories—Non-Fastboot Modes and User-Select Multiplier

Fastboot Modes.

• Non-Fastboot Modes (FASTBOOT = 0): The device operates in default PLL bypass mode during

boot. The Non-Fastboot bootmodes available on the C6421 are shown in Table 3-4.

• User-Select Multiplier Fastboot Modes (FASTBOOT = 1): The bootloader code speeds up the

device during boot. The PLL multiplier is selected by the user via the PLLMS[2:0] pins. The

User-Select Multiplier Fastboot bootmodes available on the C6421 are shown in Table 3-5.

All other modes not shown in these tables are reserved and invalid settings.

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