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SDA 6000
PRELIMINARY DATA SHEET
Version 2.1
System Control & Configuration
6 - 20
Micronas
6.7
Watchdog Timer
The watchdog timer is a 16-bit up counter which can be clocked with the CPU clock
(
f
CPU
), either divided by 2 or divided by 128. This 16-bit timer is realized as two
concatenated 8-bit timers (see
Figure 6-3
). The upper 8 bits of the watchdog timer can
be preset to a user-programmable value via a watchdog service access in order to vary
the watchdog expire time. The lower 8 bits are reset on each service access.
The following figure shows the WDT block diagram:
Figure 6-3
WDT Block Diagram
The current count value of the Watchdog Timer is contained in the Watchdog Timer
Register WDT, which is a non-bitaddressable read-only register. The operation of the
Watchdog Timer is controlled by its bitaddressable Watchdog Timer Control Register
WDTCON. This register specifies the reload value for the high byte of the timer and
selects the input clock prescaling factor.
After any software reset, external hardware reset (see note), or watchdog timer reset,
the watchdog timer is enabled and starts counting up from 0000
H
with the frequency
f
CPU
/2. The input frequency may be switched to
f
CPU
/128 by setting bit WDTIN. The
watchdog timer can be disabled via the instruction DISWDT (Disable Watchdog Timer).
Instruction DISWDT is a protected 32-bit instruction which will ONLY be executed during
the time between a reset and execution of either the EINIT (End of Initialization) or the
SRVWDT (Service Watchdog Timer) instruction. Either one of these instructions
disables the execution of DISWDT.
When the watchdog timer is not disabled via instruction DISWDT it will continue counting
up, even during Idle Mode. If it is not serviced by the SRVWDT instruction by the time
the count reaches FFFF
H
the watchdog timer will overflow and cause an internal reset.
In this case the Watchdog Timer Reset Indication Flag (WDTR) in register WDTCON will
be set.
UEB11133
WDT Control
WDT Low Byte
WDT
f
MUX
WDTIN
DISWDT
Clear
WDT High Byte
WDTREL
WDTR
2
÷
128
÷
Summary of Contents for SDA 6000
Page 3: ...Contents Overview...
Page 21: ...Pin Description...
Page 22: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Pin Descriptions 2 3 Micronas 2 Pin Descriptions...
Page 29: ...Architectural Overview...
Page 33: ...C16X Microcontroller...
Page 88: ...Interrupt and Trap Function...
Page 122: ...System Control Configuration...
Page 159: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 System Control Configuration 6 40 Micronas...
Page 160: ...Peripherals...
Page 282: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Peripherals 7 124 Micronas...
Page 283: ...Clock System...
Page 284: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Clock System 8 3 Micronas 8 Clock System...
Page 288: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Clock System 8 8 Micronas...
Page 289: ...Sync System...
Page 290: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Sync System 9 3 Micronas 9 Sync System...
Page 301: ...Display Generator...
Page 348: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Display Generator 10 50 Micronas...
Page 349: ...D A Converter...
Page 352: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 D A Converter 11 6 Micronas...
Page 353: ...Slicer and Acquisition...
Page 381: ...Register Overview...
Page 398: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Register Overview 13 20 Micronas...
Page 399: ...Elelctrical Characteristics...
Page 411: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Electrical Characteristics 14 14 Micronas...