TMS320DM6435 datasheet(71/252 Pages) TI1

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3.4.1.1 FASTBOOT

TMS320DM6435

Digital Media Processor

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SPRS344C – NOVEMBER 2006 – REVISED JUNE 2008

• Internal Bootloader ROM (0x0010 0000): For most boot modes, the DSPBOOTADDR defaults to the

internal Bootloader ROM so that the DSP can immediately execute the bootloader code in the internal

ROM. The bootloader code decodes the captured BOOTMODE, FASTBOOT, default AEM (DAEM),

and PLLMS information (in the BOOTCFG register) to determine the proper boot operation.

Note: For all boot modes that default to DSPBOOTADDR = 0x0010 0000, the bootloader code

disables all C64x+ cache (L2, L1P, and L1D) so that upon exit from the bootloader code, all C64x+

memories are configured as all RAM. If cache use is required, the application code must explicitly

enable the cache. For more information on boot modes, see Section 3.4.1, Boot Modes. For more

information on the bootloader, see the Using the TMS320DM643x Bootloader Application Report

(literature number SPRAAG0).

• EMIFA Chip Select Space 2 (0x4200 0000): The EMIFA ROM Direct Boot in PLL Bypass Mode

(BOOTCFG settings BOOTMODE[3:0] = 0100b, FASTBOOT = 0) is the only exception where the

DSPBOOTADDR defaults to the EMIFA Chip Select Space 2. The DSP begins execution directly from

the external ROM at this EMIFA space.

For more information how the bootloader code handles each boot mode, see Using the TMS320DM643x

Bootloader Application Report (literature number SPRAAG0).

When DM6435 exits pin reset (RESET or POR released), the PLL Controllers (PLLC1 and PLLC2) default

to PLL Bypass Mode. This means the PLLs are disabled, and the MXI/CLKIN clock input is driving the

chip. All the clock domain divider ratios discussed in Section 6.3.4, DM6435 Power and Clock Domains,

still apply. For example, assume an MXI/CLKIN frequency of 27 MHz—meaning the internal clock source

for EMIFA is at CLKDIV3 domain = 27 MHz/3 = 9 MHz, a very slow clock. In addition, the EMIFA registers

are reset to the slowest configuration which translates to very slow peripheral operation/boot.

To optimize boot time, the user should reprogram clock settings via the PLLC as early as possible during

the boot process. The FASTBOOT pin facilitates this operation by allowing the device to boot at a faster

clock rate.

Except for the EMIFA ROM Direct Boot in PLL Bypass Mode (BOOTCFG settings BOOTMODE[3:0] =

0100b, FASTBOOT = 0), all other boot modes default to executing from the Internal Bootloader ROM. The

first action that the bootloader code takes is to decode the boot mode. If the FASTBOOT option is

selected (BOOTCFG.FASTBOOT = 1), the bootloader software begins by programming the PLLC1

(System PLLC) to PLL Mode to give the device a slightly faster operation before fetching code from

external devices. The exact PLL multiplier that the bootloader uses is determined by the AEM[2:0] and

PLLMS[2:0] settings, as shown in Table 3-6 and Table 3-7.

Some boot modes must be accompanied with FASTBOOT = 1 so that the corresponding peripheral can

run at a reasonable rate to communicate to the external device(s).

Note: PLLC2 still stays in PLL Bypass Mode, the bootloader does not reconfigure it.

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