C509-L_97 SIEMENS [Siemens Semiconductor Group], C509-L_97 Datasheet - Page 239

• Manufacturer Part Number: C509-L_97
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

10
The C509-L includes a bootstrap mode, which is activated by setting the PRGEN pin at logic high
level at the rising edge of the RESET or the HWPD signal (bit PRGEN1=1). In this mode software
routines of the bootstrap loader, located at the addresses 0000 H to 01FF H in the boot ROM will be
executed. Its purpose is to allow the easy and quick programming of the internal XRAM (F400 H to
FFFF H ) via serial interface while the MCU is in-circuit. This allows to transfer custom routines to the
XRAM, which will program an external 64 KByte FLASH memory. The serial routines of the
bootstrap loader may be replaced by own custom software or even can be blocked to prevent
unauthorized persons from reading out or writing to the external FLASH memory. Therefore the
bootstrap loader checks an external FLASH memory for existing custom software and executes it.
The bootstrap loader consists of three functional parts which represent the three phases as
described below.
10.1 General Functions of the Bootstrap Loader
Phase I : Check for existing custom software in the external FLASH memory and execute it.
Phase II : Establish a serial connection and automatically synchronize to the transfer speed (baud
Phase III : Perform the serial communication to the host. The host controls the bootstrap loader by
The 3 phases of the bootstrap loader program and their connections are illustrated in figure 10-1.
Semiconductor Group
The Bootstrap Loader
rate) of the serial communication partner (host).
sending header informations, which select one of four operating modes.
These modes are:
Mode 0: Transfer a custom program from the host to the XRAM (F400 H - FFFF H ).
Mode 1: Execute a custom program in the XRAM at any start address from F400 H to
Mode 2: Check the contents of any area of the external FLASH memory by calculating
Mode 3: Execute a custom program in the FLASH memory at any start address
This mode returns to the beginning of phase III.
FFFF H .
a checksum. This mode returns to the beginning of phase III.
beyond 0200 H (at addresses 0000 H to 01FF H the boot-ROM is active).
10-1
Bootstrap Loader
1997-10-01
C509-L