Specifications

2.16 Watch dog Timer Con figu ra tion
The EBC- BX board fea tures a power- on volt age de tect, and power- down/power brown out re set
cir cuit to pro tect mem ory and I/O from faulty CPU op era tion dur ing pe ri ods of il le gal volt age lev els.
This su per vi sor cir cuitry also fea tures a watch dog timer which can be used to guard against soft ware
lock ups. An in ter nal timer with a pe ri od of 1.5 or 150 sec onds will, when en abled, re set the CPU if the
watch dog has not been serv iced within the al lot ted time. The watch dog timer powers- up dis abled and
must be en abled in soft ware bef ore tim ing will be gin. Ena bling is ac com plished by writ ing a 1 to I/O
port 1EEH. Writ ing a 0 to I/O port 1EEH will dis able the watch dog. Af ter ena bling, pet ting may be ac -
com plished by writ ing any value to I/O port 1EFH at least every 1.5 if J21 is not jumpered or at least
every 150 sec onds if J21 is jumpered, or a re set will oc cur. This mode of op era tion can be used with the
BIOS or DOS pro vided that the watch dog is dis abled bef ore mak ing any ex ten sive BIOS or DOS calls,
es pe cially video or disk I/O calls which could ex ceed the time sec onds al lowed when the 1.5 sec ond
mode is used.
2.17 Status LED
A green LED is popu lated on the board at D1 which can be used for any ap pli ca tion spe cific pur -
pose. The LED can be turned on in soft ware by writ ing a 1 to I/O port 1EDH. The LED can be turned off
by writ ing a 0 to 1EDH.
2.18 Bat tery Se lect Con trol
An on board 350mAH nomi nal ca pac ity, lith ium bat tery is pro vided for the CMOS Clock/Cal en dar.
A mas ter bat tery en able jumper is pro vided at J27. When J27 is jumpered pins 2-3, bat tery power is
sup plied to the Clock/Cal en dar. When J27 is jumpered pins 1-2, the bat tery is to tally dis con nected and
no cur rent will be drawn from it. Bat tery life is highly de pend ent upon duty cy cle as there is no cur rent
drawn from the bat tery when +5 volts is ap plied to the board. Both stor age and op era tional tem pera tures
play a promi nent fac tor in bat tery life. High tem pera tures will shorten bat tery life sig nifi cantly. J27
must be jumpered 1-2 if a bat tery is not in stalled.
Page 2 - 16 OPERATIONS MANUAL EBC-BX 030923
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J21
Watch dog Timer con figu ra tion jumper J21