![5.6.Timers and Counters](/images/new-backgrounds/120273/12027355x1.webp)
MSB900/L Detailed Technical Manual V1.0 |
5.6.Timers and Counters
5.6.1.Programmable Timers
An 8253 compatible timer/counter device is also included in the board's ASIC device. This device is utilized in precisely the same manner as in a standard AT implementation. Each channel of the 8253 is driven by a 1.190 MHz clock, derived from a 14.318 MHz oscillator, which can be internally divided in order to provide a variety of frequencies.
Timer 2 can also be used as a general purpose timer if the speaker function is not required.
Timer Assignment
Timer
Function
0
1
2
DRAM refresh request timing (15 µs)
Speaker tone generation time base
5.6.2.RTC (Real Time Clock)
An AT compatible date/time clock is located within the chipset. The device also contains a CMOS static RAM, compatible with that in standard ATs. System configuration data is normally stored in the clock chip's CMOS RAM in a manner consistent with the convention used in other AT compatible computers. To attach an external battery on a MSB900L board refer to section 2.11.1.
5.6.3.Watchdog
The watchdog timer detects a system crash and performs a hardware reset. After power up, the watchdog is always disabled as the BIOS does not send strobes to the watchdog. In case the user wants to take advan- tage of the watchdog, the application must produce a strobe at least every 800 ms. If no strobe occurs within the 800 ms, the watchdog resets the system.
For more information, please refer to the driver/software/BIOS manual
There are some programming examples available:
Product
5.6.4.ROM-BIOS Sockets
An EPROM socket with 8bit wide data access normally contains the board’s AT compatible
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