C509-L_97 Datasheet, PDF (262/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Bootstrap Loader
C509-L
Figure 10-20
Bootstrap Loader Flowchart of Operating Mode 1
10.4.2.3 Selection of Operating Mode 2
Mode 2 is used to calculate a checksum of an external FLASH memory sector beginning at a
startaddress with the specified length datalength. The header block, which has to be prepared
and sent by the host for the activation of operating mode 2 is shown in figure 10-21.
Figure 10-21
Header Block for Operating Mode 2
The operating mode 2 header block transfers the 16-bit startaddress of the external FLASH
memory block, which has to be checked, the number of bytes (datalength), which have to be
checked beginning at startaddress, a dummy byte, and a checksum byte.
Mode 2 calculates a checksum of any area of the external FLASH memory starting at startaddress
with a length of datalength (see also section 10.2.2). The endaddress of the corresponding
memory block is startaddress + datalength. The two calculated checksum bytes are compared
with two fixed checksum values which must be placed at the end of the checked external FLASH
memory block, that is at addresses startaddress + datalength + 1 and startaddress + datalength
+ 2. If these checksum values are equal to the calculated checksums, an acknowledge byte (55H)
is sent to the host. Otherwise the checksum error code (FEH) is transmitted to the host.
Semiconductor Group
10-24
1997-10-01