Advantech ITA-5831 Series, Руководство пользователя

Страница: 86 / 96

ITA-5831 User Manual 76
A.1 Programming the Watchdog Timer
The ITA-5831’s watchdog timer can be used to monitor the software operations and
take corrective action if the software fails to function within the programmed period.
This section describes the operation of the watchdog timer and procedures for pro-
gramming it.
A.1.1 Watchdog Timer Overview
The watchdog timer is built into the embedded controller and provides the following
user-programmable functions:

Can be enabled/disabled via software
 Timebase is 100 ms

Each time limit is a word long
 The event time can be set from 0 to 0xFFFE

Writing 0xFFFF to time limit ram will disable events
 The timer can be set from 100 ms to 109.22 minutes

Generates and resets signal if the software fails to reset the timer before timeout
A.1.2 Programming the Watchdog Timer
The watchdog timer logic can be accessed through the EC PM2 (power management
channel 2). PM2 is a LPC I/O port channel. The PM2 channel includes one com-
mand/status port and one data port. The system can use the command port to send a
command to the EC or obtain the current port status. The system can send command
parameters or obtain the EC return data through the data port. Typically, 0x29A is the
command/status port and 0x299 is the data port.
Command/Status Port: Port 0x29A
Action Description
Write
Send command to EC
Read Get EC 299/29A port status
The status that was read from 0x29A is described below.
Status from command/status port
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
X X X X X X IBF (Input buffer full) OBF (Output buffer full)
Note! 1. BIT 0 (OBF) - When the EC returns data to the 0x299 port, the OBF
is set as “1”. The OBF is cleared to zero after the system reads
data from the 0x299 port.
2. BIT 1 (IBF) - When the system writes data or commands to 0x299
or 0x29A, the IBF is set as “1”. The IBF is cleared to zero after the
EC obtains data/command from the 299/29A port.