Cpu Supervisor; Figure 2: Cpu Supervisor - Semtech SH3000 User Manual

2. CPU Supervisor

The SH3000 has two CPU Supervisor functions that manage the reset of the host microcontroller, a low-
V monitor (brownout detector) and a watchdog timer (see Figure 2).
DD
Both functions are integrated with the Clock Management System to provide a more complete system
solution than stand-alone components.
The SH3000 has both active high and active low reset output pins. Both are driven strong in the active
state, and weak in the inactive state. This eliminates the need for external pull-ups and allows various
reset sources to be connected together in a wire-OR configuration. (this makes it simple to set up a
manual rest circuit.)
A set of flags in the ResetEvent register (R0x1B) indicates the source of the reset to the system software.
Noise Filter
V
DD
1
4.40 V
Temperature-
V
HIGH
compensated
Threshold
Voltage
D/A
2.30 V
Reference
V
LOW
Lock Logic
6-bit Value
SH3000UM version 0.95
Copyright ©2002 Semtech Corporation
PWR
R
ESET
CLK
OUT
32kHz
Hysteresis
50mV .
TYP
Write-once
Initialization Logic
Mode

Figure 2: CPU Supervisor

2002-08
32kHz
Reset Logic
&
OK
Minimum
Duration Timer
1 → 0
U
NDERFLOW
7-bit Down Counter
/256
/128
7-bit Watchdog
Timeout Value
SH3000 User Manual
Preliminary
R
ESET
RST
V
DD
11
20
K
20
K
RST
N
10
Watchdog
Reload Control
Load
Alternating Codes
Logic
0x5A / 0xC3
From / To
Serial I/O
4