Real Time Clock; Watchdog Timer - Technologic Systems TS-2200 User Manual

TS-2200 User's Manual
A standard packet driver is installed on the board by default, along with a few sample network
applications written with the public domain Waterloo TCP/IP software (WATTCP). WATTCP is a freely
available package (including source code) that provides TCP/IP connectivity for programs written for
the DOS environment.
During POST, the BIOS initializes the CS8900A registers with the correct settings – interrupt IRQ12,
I/O address range 300h – 30Fh, and I/O mapped operation. The DOS packet driver is loaded by
AUTOEXEC.BAT once DOS starts. To run the sample programs (ping and finger) on the TS-2200, first
examine the contents of the WATTCP.CFG configuration file in the A:\ETHERNET directory and
correct any information that is not valid for your particular network. Then simply run a sample program
from the DOS command line. For example:
[A:\]ping www.embeddedx86.com
Technologic Systems Example Configuration
Pinging 'www.embeddedx86.com' [209.130.84.83]
sent PING # 1 , PING receipt # 1 : response time 0.00 seconds
Ping Statistics
Sent
Received
Success
Average RTT : 0.35 seconds
[A:\]
If you prefer to use a package other than WATTCP, go right ahead. Device-drivers for other operating
systems and network protocols are available from both the Technologic Systems and Cirrus Logic
web sites (see Appendix H below).

9 Real Time Clock

The Dallas Semiconductor DS12887 is used for the PC compatible battery-backed real-time clock. It is
a completely self-contained module that includes a Motorola 146818 compatible clock chip, the
32.768 kHz crystal, the lithium battery, and 114 bytes of battery-backed CMOS RAM. It is guaranteed
to maintain clock operation for a minimum of 10 years in the absence of power. It is located at the
standard PC I/O addresses of Hex 070 and 071. The top 32 bytes (index 60h through 7Fh) are not
used by the BIOS and are available for user applications.

10 Watchdog Timer

The Intel 386EX contains a 32-bit watchdog timer (WDT) unit that can be used in two different modes
to effect a watchdog supervisory function. In either mode, a system reset is asserted when the WDT
times out preventing a system "hanging" due to a software bug. To prevent a WDT timeout, the
application must periodically "feed" the WDT by writing to specific I/O locations. The 32-bit down-
counter allows timeout values as high as 160 seconds.
The general-purpose timer mode is more flexible in that the timeout values can be changed
dynamically and the timer can be turned on and off under software control. The disadvantage of this
mode is that it doesn't provide 100% protection because a bug could turn off the timer during a crash
and the system would hang.
The software secure watchdog mode utilizes a "lockout sequence" to set a WDTEN bit in the watch-
dog status register. Once this bit is set, only a system reset can clear this bit. When WDTEN is set, it
is not possible to change the WDT timeout value or to turn off the WDT. This provides a high level of
assurance against errant software causing a system to hang.
For details see the Intel 386EX User Manual.
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Technologic Systems
11/06/2000