Siemens ERTEC200 - Manual (Page 46)

4.5.6 Watchdog Registers
The watchdog registers are 32 bits in width. For read/write access of the watchdog registers to be meaningful, a 32-bit
access is required. However, a byte-by-byte write operation is not intercepted by the hardware.
To prevent the watchdog registers from being written to inadvertently, e.g., in the event of an undefined computer crash,
the writable watchdog registers are provided with write protection. The upper 16 bits of the registers are so-called key
bits. In order to write a valid value in the lower 16 bits, the key bits must be set to 0x 9876 yyyy (yyyy is the 16-bit value
to be written).
4.5.7 Address Assignment of Watchdog Registers
Watchdog (Base Address 0x4000_2100)
Register Name Offset Address Address Area Access Default Description
CTRL/STATUS 0x0000 4 bytes R/W 0x00000000 Control/status register WD
RELD0_LOW 0x0004 4 bytes R/W 0x0000FFFF Reload register 0_Low Bits 0-15
RELD0_HIGH 0x0008 4 bytes R/W 0x0000FFFF Reload register 0_High Bits 16-31
RELD1_LOW 0x000C 4 bytes R/W 0x0000FFFF Reload register 1_Low Bits 4-19
RELD1_HIGH 0x0010 4 bytes R/W 0x0000FFFF Reload register 1_High Bits 20-35
WDOG0 0x0014 4 bytes R 0xFFFFFFFF Watchdog timer 0 value register
WDOG1 0x0018 4 bytes R 0xFFFFFFFF Watchdog timer 1 value register
Table 12: Overview of WD Registers
4.5.8 Watchdog Register Description
CTRL/STATUS R/W Addr.: 0x4000_2100 Default: 0x0000_0000
Description Control/status register Configuration and control bits for the watchdog.
Bit No. Name Description
0 Run/xStop_V0 Enable/disable watchdog counter 0:
0: Watchdog counter 0 disabled
1: Watchdog counter 0 enabled
Note: If this bit = 0, the WDOUT0_n output of the ERTEC 200 is active (0),
the interrupt of the watchdog (WDINT) is “0”, and the status bit of counter 0
(Bit 3) is “0”.
1 Run/xStop_Z1 Enable/disable watchdog counter 1:
0: Watchdog counter 1 disabled
1: Watchdog counter 1 enabled
Note: If this bit = 0, the WDOUT1_N output of the ERTEC 200 is passive (1)
and the status bit of counter 1 (Bit 4) is “0”.
2 Load(Trigger) Watchdog trigger (load watchdog counters 0 and 1 with the value of the
effect at the instant of writing.
the watchdog counter; a
unters.
reload registers):
0: Do not trigger watchdog
1: Trigger watchdog
While this bit can be read back, it only has an
Writing a value of 1 to this bit is sufficient to trigger
0/1 edge is not needed.
The trigger signal acts on both watchdog co
3 Status_Counter 0 Watchdog status counter 0 (writing is ignored):
0: Watchdog counter 0 has not expired
1: Watchdog counter 0 has expired
Note: This bit can only be read as ‘1’ if Run/xStop_Z0 is active (1).
4 Status_Counter 1 Watchdog status counter 1 (writing is ignored):
0: Watchdog counter 1 has not expired
1: Watchdog counter 1 has expired
Note: This bit can only be read as ‘1’ if Run/xStop_Z1 is active (1).
15-5 Reserved Not relevant (read=0)
31-16 Key bits Key bits for writing to this register (read=0).
If bits 31-16=9876h, writing of bits 0-4 of this register has an effect;
otherwise, no effect.
Copyright © Siemens AG 2007. All rights reserved. 46 ERTEC 200 Manual
Technical data subject to change Version 1.1.0