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B
attery
B
ackup
a
nd R eset
HP 8110 Α Service G uide
data sett ings to th at he ld in
t
he Flash
EEPRO Ms
14- Fl ash EPR O M s
Co ntain the firmware t hat is used to specify
a
nd
contro l the HP 8110Α
15-Stat i c RAM s
Co ntain data that is regul arly
c
hanging
More detail ed descriptions of the funct i onal uni ts
f
ollow:
Thi s secti on i s on sche matic 3Α.
Wh en p ower is first applied to t he Micro p rocessor B oard, t he timer
for m ed b y U 13 a nd associated comp onents hol ds the MPU Reset lin e
do wn for α
p
eriod exceeding 100ms . Thi s all o w s tim e
f
or α general
MPU reset and α lo nger
p
eriod
f
or th e MPU
c
lock PLL to stabi lise .
The Stat ic RAM S (3 Ε ) are
b
acked by the batter y when p ower
i s not
b
e ing a pplied to the instrument, and du ring reset .
U
13
di sconn ects th e battery
a
nd enabl es th e
P
ower S upply vi a Q1 wh en
t h e in strum en t
i
s
p
owered, and after reset .
B
oot Control
Thi s sect i on i s on sche matic 3Α.
If t he
f
ront p a n el numeric keys 0 and 0 are hel d
p
ressed during
s wi tch -on , t he s y ste m is
B
ooted
f
rom
t
he Mem ory Card in stead o f
t
h e Fl ash EPROM S .
U
29 B gates t h e t wo key board si gn als together an d sets D fl ip flop
U27 A .
D
ata
f
rom
t
he flip flop controls t he multipl exer
U
14, whi ch
e
nables the Mem ory Card buffered control signals ( U 31) .
If t hese key s are not
p
ressed during switch-on,
U
29 e na bl es the Flash
EPR OM s.
During MPU reset the general-purpose ΙΟ lines are regarded as
input li n es. After reset the y are config ured as required by takin g
l ow certain lin es on t he MPU Databus, whi ch are t hen used as mode
sel ect lines for the general-pu rp ose ΙΟ lines . In t his case, lin es 4 an d
9 are ta ken l ow by U 39 A ,
U
39D
a
nd
U
39 E .
Oscillator
Thi s secti on i s on sche matic 3Α.
Th e MPU i s c l oc ked by an internal PLL oscill ator, us ing an external
cry stal . The crystal oscillates at 32 .768kH z,
p
roducing final operat ing
f
requen ci es of 8 .38 MHz
d
uring reset and 16.78 MHz during normal
o
p eratio n . The cr ystal, Υ1,
i
s tune d
b
y R10/R11 and C47, C48.
Fun ctional Desc ription 7-1 5
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