MB86391 Datasheet, PDF (47/69 Pages) Fujitsu Component Limited. – MPEG2 1chip Audio/Video Encoder

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3.8.1 Downloading from the External ROM
This mode downloads the program from an external ROM to the SDRAM. When the boot
program of the internal ROM confirms of the external ROM, start downloading from the external
ROM to SDRAM via MB86391. After downloading, MB86391 starts the program on SDRAM.
When the existence of an external ROM is confirmed, the program re−sets the wait count
specified with "wait" in the header to download the data to be downloaded. The download data
configuration is not dependent on the ROM bus width.
3.8.2 Serial Download
The internal ROM boot program of the MB86391 sets to either serial API or SDRAM direct
download mode (see Chapter 3.8.3) if it confirms that there is no external ROM.
Upon arrival of an interrupt from the serial interface, the internal ROM boot program of the
MB86391 receives the data transferred with the serial interface and, if the header of this data is
configured as shown in Table 3.8.2a, downloads it as serial API.
The internal serial interface of the MB86391 supports Data32 and ASCII send and receive data
formats (see Chapter 3.2). Since data can also be sent with SCLK synchronization or
Asynchronization (9,600bps), four types of serial booting are available (Data32/SCLK
synchronization, ASCII/SCLK synchronization, Data32/Asynchonization, and
ASCII/Asynchronization).
3.8.3 Direct SDRAM Downloading
The SDRAM connected to the MB86391 host/SDRAM is assigned in the CS1 space by the
internal ROM boot initialization routine. From the host interface with the parallel API, the entire
SDRAM area is accessible if used with a bank register. This enables to write the program and
data (including the header in Table 3.8.3) from the host/SDRAM interface to the SDRAM by
directly accessing the memory.
During this period, the internal ROM boot program of the MB86391 is in an infinite loop waiting for
interruption. Therefore, from the host/SDRAM interface, instruct to start the program by
executing parallel API interruption (by writing to the register) after direct downloading to the
SDRAM is complete.
The internal ROM boot program of the MB86391 verifies that the appropriate header is in from
the SDRAM leading address and then jumps to the Entry Address to start executing the program.
MB86391
Product Specification
Rev. 1.1
12, November 2001
43