C509-L_97 Datasheet, PDF (261/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Bootstrap Loader
C509-L
10.4.2.2 Selection of Operating Mode 1
Mode 1 is used to execute a custom program in the XRAM of the MCU at a given start address. The
header block, which has to be prepared and sent by the host for the activation of operating mode 1
has the structure as shown in figure 10-18.
Figure 10-18
Header Block for Operating Mode 1
The operating mode 1 header block transfers the 16-bit XRAM startaddress for program execution
in the XRAM, three dummy bytes, and a checksum byte.
After sending the appropriate header block for mode 1, no further serial communication is
necessary. The block diagram for the communication between the host and the MCU is shown in
figure 10-19:
Figure 10-19
Operating Mode 1 Communication Structure
Mode 1 swaps the XRAM to code memory by setting the corresponding swap-bit in SFR SYSCON1
and starts the program execution in the XRAM at any start address given in the header block at
startaddress.
Note: If the supported interrupts TIMER 0 and SINT 0 are used as described in section 10.1, the
XRAM area from F400H to F41FH is reserved for interrupt handling routines. Therefore
startaddress has to be greater than or equal to F420H.
The corresponding bootstrap loader flowchart of mode 1 is shown in figure 10-20.
Semiconductor Group
10-23
1997-10-01