USBB17AP77016-XXX-B11 NEC Electronics, USBB17AP77016-XXX-B11 Datasheet - Page 37

• Manufacturer Part Number: USBB17AP77016-XXX-B11
• Description: DSP middleware(WMA (Windows Media Audio)decoder)
• Manufacturer: NEC Electronics

[Processing]
• case000 label:
• case001 label:
• case002 label:
• get_data label:
• get_data_next label:
• set_data label:
• finish label:
The value of the FileCBGetData_fp variable is compared with the value r1 of the requested offset position and
branching to the following label occurs depending on the result:
Branching to this label occurs if either of the first two bytes of input data received first via the host interface
matches the requested offset data. The value of the write_ptr variable is then set to the read_ptr variable. The
size of the data to be received via the host interface in the processing following the get_data label is also set, and
the program jumps to the get_data label.
Branching to this label occurs if data in front of the input data already received is requested. In this case, the
data up to the requested offset data is received via the host interface. The data received here is not used and is
therefore not saved in the input data receive buffer.
The value of the write_ptr variable is then set to the read_ptr variable. The size of the data to be received is also
set, and the program jumps to the get_data label.
Branching to this label occurs if the requested offset data has already been received. In this case, the read_ptr
variable is set, but because the data already received is set in the input buffer, the position that is the value of the
write_ptr variable rewound by the required number is set.
Next, if data of the requested size can be set in the input buffer from the data already received, the program
jumps to the set_data label, and if data of the requested size cannot be set in the input buffer from the data
already received, a new receive data size is set and the program jumps to the get_data label.
If the requested size is 128 bytes or less, the program jumps to the get_data_next label. In other cases, input
data is received via the host interface, but this data is not used and is therefore not saved in the receive buffer.
When the receive processing is finished, the program jumps to the finish label.
If the size of the data that should be received is 0, the program jumps to the set_data label. In other cases, the
input data is received via the host interface and stored from the position indicated by the write_ptr variable.
When the receive processing is finished, the write_ptr variable is updated and the program performs set_data
label processing.
The input data stored in the input data receive buffer is read out from the position indicated by the read_ptr
variable and set in the input buffer in accordance with the requested conditions. The program then performs
finish label processing.
After processing such as setting the return values and updating the FileCBGetData_fp variable is finished, the
program returns to the caller from the wmad_FileCBGetData function processing.
Branch to the case000 label if FileCBGetData_fp = r1
Branch to the case001 label if FileCBGetData_fp < r1
Branch to the case002 label if FileCBGetData_fp > r1
CHAPTER 4 SYSTEM EXAMPLE
User’s Manual U15683EJ1V0UM
37