B-Record Example
MOTOROLA
Bootstrap Mode Operation
9-3
9.1.3 Registers Used in Bootloader Program
The bootloader program uses general-purpose registers r5 to r12 as well as r13 as the return register and
r14 as the link register. All the other registers can be used by target programs.
9.1.4 Setting Up the RS-232 Terminal
To set up communication between your target system and the PC, set the communication specifications to
the baud rate desired, no parity, 8-bit character length, and 1 stop bit. You may pause after each line
(b-record) is transferred to make sure each transferred ASCII character is echoed.
After setting up the hardware, powering up the system, and entering bootstrap mode, send an
a
or
A
character to the target system to initiate the link. Once the bootloader receives this character, it adjusts the
baud rate. If the link is successful, the bootloader will return the special character
:
(colon) as an
acknowledgment.
9.1.5 Changing the Speed of Communication
You can change the communication baud rate after communication is set up in the RS-232 terminal.
Simply issue a b-record to re-initialize the baud control register of the UART controller. After the last
character of this b-record is sent, the echo of this last character will be transmitted at the new speed. The
maximum speed recommended for Bootstrap is 57600 baud.
9.2 B-Record Example
Before you can download a program to system memory, the target system may need to be initialized using
the internal registers. An init file can be built using a text editor. Code Example 9-1 initializes the eSRAM
memory location0x00310000 to 0x12345678 in word access mode, the location0x00310006 to 0x7788 in
half-word access mode, and the location0x00310009 to 0x55 in byte access mode.
Code Example 9-1. init.b Example
// init.b -- Initialization Example
00310000C412345678initialize 0x00310000 to 0x12345678
00310006427788
initialize 0x00310006 to 0x7788
003100090155
initialize 0x00310009 to 0x55
With b-records similar to those stated above, a target program can be downloaded to memory and executed
from the address chosen with the following b-record:
1122334400
execute from 11223344
The target program may exit and return to the bootloader program by jumping to address 0x00000100,
where the bootloader program starts.
9.3 Instruction Buffer Usage
An 8-word instruction buffer is provided for ARM920T core vector table storage, instruction and data
storage. The buffer starts at 0x00000004. Up to eight instructions can be loaded to the instruction buffer for
execution.Usually, the last instruction is an unconditional jump instruction (jmp) that jumps to the start of
the bootloader program (0x00000100).
Содержание DragonBall MC9328MX1
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