at75c1222 ETC-unknow, at75c1222 Datasheet - Page 6

• Manufacturer Part Number: at75c1222
• Manufacturer: ETC-unknow

Upload Process
Binary Image Format
Table 1. Binary Image Fields
Dual-port Mail Box
Configuration
6
Field Name
INIT_OFFSET
INIT_LENGTH
SW_OFFSET
SW_LENGHTH
INIT_CODE
SW_CODE
AT75C1222
Offset from Start of File (Bytes)
16 + 2*INIT_LENGTH
12
16
0
4
8
A typical DSP program uses a number of initialized variables. Typically, the initial values
are stored in the program space, and copied into their RAM location by the DSP start-up
routine. This leads to the following statements:
•
•
•
•
•
The mailbox operation and status messages are described in the section “Mailbox
Usage” on page 7.
When the system is idle, the AT75C1222 module is stored in the ARM memory space,
possibly in non-volatile memory. The module contains the data initialization code, the
application code, and additional formatting data. The various fields of the AT75C1222
binary image are described in Table 1.
The dual-port mail box (DPMB) is programmed in configuration 0 (as defined in the
AT75C DSP Subsystem Datasheet) and gives the configuration shown in Table 2 on
page 7. All the mailboxes allow read/write access from both sides. Arbitration is done
using the semaphores.
Just after the boot routine has initialized the variables, the DSP subsystem exhibits
high redundancy since the same values exist in both program and data memories.
The initial values stored in the program memory waste space and are not used
during operation.
To improve the program memory usage, the software is loaded in two consecutive
steps.
A small data initialization program is first loaded and executed. This program just
initializes the X- and Y-RAM to the values expected by the audio decoder software.
When the initialization is done, the program sends a DATA_INIT_DONE status
message to the ARM application through the status mailbox.
Then, the DSP subsystem is put in reset and the program itself is loaded. This code
has no data init start-up routine. It assumes the RAMs are already initialized, which
saves program space. When the software is ready to work, it sends a
SW_INIT_DONE status message through the status mailbox.
2*INIT_LENGTH
2*SW_LENGTH
Length (Bytes)
4
4
4
4
Description
Defines the position of the data initialization code from
the beginning of the module image.
Defines the length of the data initialization code (16-bit
words). Valid between 0 and 24576.
Defines the position of the audio decoder program
from the beginning of the module image.
Defines the length of the audio decoder code (16-bit
words). Valid between 0 and 24576.
Binary code of the application program.
Binary code of the data initialization program.
2664A–INTAP–07/02