The following sections discuss in detail the different boot modes available and the process used for loading data
code into the device.
2.2.2 Bootloader Device Configuration
At reset, any C28x CPU-based device is in C27x object-compatible mode. It is up to the application to place the
device in the proper operating mode before execution proceeds.
On the C28x devices, when booting from the internal boot ROM, the device is configured for C28x operating
mode by the boot ROM software. You are responsible for any additional configuration required.
For example, if your application includes C2xLP source, then you are responsible for configuring the device for
C2xLP source compatibility prior to execution of code generated from C2xLP source.
The configuration required for each operating mode is summarized in
.
Table 2-2. Configuration for Device Modes
C27x Mode (Reset)
C28x Mode
C2xLP Source
OBJMODE
0
1
1
AMODE
0
0
1
PAGE0
0
0
0
M0M1MAP
1
1
1
Other Settings
SXM = 1, C = 1, SPM = 0
(1)
C27x refers to the TMS320C27x family of processors. C2xLP refers to the TMS320F24x/
TMS320LF240xA family of devices that incorporate the C2xLP core. The information in
is
for reference only and is not applicable for the typical user development. For more information on
the C2xLP core, refer to the
TMS320C28x DSP CPU and Instruction Set Reference Guide
(2)
Normally for C27x compatibility, the M0M1MAP would be 0. On these devices, however, it is tied off
high internally; therefore, at reset, M0M1MAP is always configured for C28x mode.
2.2.3 PLL Multiplier and DIVSEL Selection
The Boot ROM changes the PLL multiplier (PLLCR) and divider (PLLSTS[DIVSEL]) bits as follows:
•
All boot modes:
PLLCR is not modified. PLLSTS[DIVSEL] is set to 3 for SYSCLKOUT = CLKIN/1. This
increases the speed of the loaders.
Note
The PLL multiplier (PLLCR) and divider (PLLSTS[DIVSEL]) are not affected by a reset from the
debugger. Therefore, a boot that is initialized from a reset from the Code Composer Studio™ IDE may
be at a different speed than booting by pulling the external reset line (XRS) low.
The reset value of PLLSTS[DIVSEL] is 0. This configures the device for SYSCLKOUT = CLKIN/4 .
The boot ROM will change this to SYSCLKOUT = CLKIN/1 to improve performance of the loaders.
PLLSTS[DIVSEL] is left in this state when the boot ROM exits and it is up to the application to change
it before configuring the PLLCR register.
The boot ROM leaves PLLSTS[DIVSEL] in the CLKIN/1 state when the boot ROM exits. This is not
a valid configuration if the PLL is used. Thus, the application must change it before configuring the
PLLCR register.
2.2.4 Watchdog Module
When branching directly to Flash, OTP, or M0 single-access RAM (SARAM) the watchdog is not touched. In the
other boot modes, the watchdog is disabled before booting and then re-enabled and cleared before branching
to the final destination address. In the case of an incorrect key value passed to the loader, the watchdog will be
enabled and the device will boot to flash.
Boot ROM
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
203
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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