Entering Bootstrap Mode; Table 9-1 Bootstrap Record Format; Table 9-2 Definition Of Count/Mode Byte - Motorola DragonBall MC9328MX1 Reference Manual

Bootstrap Mode Operation

9.1.1 Entering Bootstrap Mode

Bootstrap mode is the debug mode of the MC9328MX1. To enter bootstrap mode, the BOOT pins must be
properly configured during system reset. After reset, the bootstrap ROM is selected for reset vector fetch
cycles. Please refer to Section 8.2, "System Boot Mode Selection," on page 8-7 for details about
configuring bootstrap mode.
9.1.2 Bootstrap Record Format
Only bootstrap records (b-records) are accepted for data transfers in bootstrap mode. The b-record format
is shown in Table 9-1, and Table 9-2 further defines the COUNT/MODE byte. All b-records are in
uppercase. Each byte is represented by two ASCII characters during transfer (for example, a byte of value
0x12 will be represented by the characters
Bit(s)
7–6
5
4–0
1. A half-word is defined as 16 bits, while a word is defined as 32 bits.
2. The address specified must fall on a data size boundary: for word access, the last 2 bits of
the address must be 0, while for half-word access, the last bit of the address must be 0. The
data count in the COUNT/MODE byte must be a multiple of the data size: for word access,
the data count must be a multiple of four, while for half-word access, the data count must
be in multiple of two. If either the address or the data count is not on an appropriate data
size boundary, the bootloader program will return a
error has occurred, and the bootloader will then start waiting for a new b-record.
3. During a read operation, a
returned.
4. A data count of zero (disregard the value of data size and the status of the mode flag) has a
special meaning: execute from the address specified. In this case, no data will follow the
COUNT/MODE byte.
Comments can be added to files of b-records. As described above, the shortest b-record consists of 10
ASCII characters (when the data count is 0) of 0 to 9 or A to F (hexadecimal digits). Comments included
must not contain patterns to prevent the comments from being considered a b-record.
9-2
).
12
Table 9-1. Bootstrap Record Format
4 Bytes 1 Byte
Address Count/mode
Table 9-2. Definition of COUNT/MODE Byte
Definition
Data size
Read/write flag
Data count in number of bytes
NOTE:
character (forward slash) is returned after the last data has been
/
MC9328MX1 Reference Manual
N (Count) Bytes
Data
Settings
00 = Byte
01 = Half-word
10 = Reserved
11 = Word
0 = Write
1 = Read
Value from 0 to 31
character (asterisk) to indicate that an
*
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