C509-L_97 Datasheet, PDF (255/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Bootstrap Loader
C509-L
10.4.2 Operating Mode Selection
When the bootstrap loader enters phase III, it first waits for an eight byte long header block from the
host, which will be confirmed with an acknowledge byte (55H). The header block contains the
information for the selection of the operating mode. Depending on this data the bootstrap loader
selects and activates the desired operating mode. This select procedure shows the block diagram
in figure 10-12.
Figure 10-12
Operating Mode Selection Procedure
If the MCU receives an incorrect header block, e.g. because of a bad serial transmission, the
bootstrap loader sends, instead of an acknowledge byte, a checksum- or block error byte (see
table 10-3) to the host and awaits the header block again. In this case the host may react by
resending the header block or by releasing a message to the customer.
The flowchart in figure 10-13 shows the structure of the phase III bootstrap loader part in detail.
Semiconductor Group
10-17
1997-10-01