Acer AL502 Service Manual page 4

8. E 2 PROM (Circuit diagram MAIN PWB)
Data tran s fer bet ween I304 an d CPU (Circu i t diag ram MAIN PWB p ag e 4/ 7 (I303) is e ffecte d th rou g h th e IIC
bu s SCL (pin 9) an d SDA (pin 8) of I300 o r SCL (pi n 42) an d SDA pin 39 of I301. Th e da ta to be tran sferred to
each d ev ice are stored in I304.
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I300 con trol data.
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OSD related s ettin g data.
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Oth er con trol data for serv ice men u .
9. CPU circuit (Circuit diagram MAIN PWB)
I303 (MT V312M64) (SM89516C25) o r (W78E62BP-40) fu n cti on s as th e CPU.
Th e sou rc e v oltag e for th e dev ice is 5.0V an d th e sy stem clock frequ en cy is 12MHz.
9.1 Detection of POW ER switch statu s
Th e CPU iden tifies th e ON statu s of th e two power su pp lies. Th e iden tification is made wh e n th e power su pply
is tu rn ed off. For example, if th e power su pply is tu rn ed off with th e POWER switch , th e POWER switch mu st be
tu rn ed on wh en ac tiv atin g t h e power su pply ag ain . If th e po wer su pply is tu rn ed o ff by pu ll in g ou t th e power
cord , th en th is power s u pply can be tu rn ed on by con n e ctin g th e power cord, wit h ou t pressin g th e POWER
switch .
9.2 Displ ay mode i den tific ation
9.2.1 Fu n ction s
(1) Display mode id en tifica tion
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Th e display mode of in pu t sig n al is iden tified based on Table 1, an d accordin g to th e frequ en cy an d polarity
(HPOL, VPOL) of h orizon tal or v ertical sy n c sig n al, presen ce of th e h orizon tal or v ertical sy n c sig n al, an d th e
di sc rimin a ti on sig n a l (HSYNC_DETECT, VSYNC_DETECT ).
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Wh en th e mode h as been identified th rou g h th e measu remen t of h orizon tal an d v ertical frequ en cies, th e total
n u mber of lin es is determin ed with a formu la of " Horizon t al frequ en c y / Vertic al frequ en c y = Total n u mber
of lin es. " Fin al i den t ific atio n ca n be mad e by exa min i n g t h e c oin c iden ce o f th e ob tain ed f ig u re wi th t h e
n u mbe r of lin es for th e mode iden t ified from th e frequ en cy .
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Wh en th e detected frequ en cy if th e sy nc sig n al h as ch an g ed, th e total n u mber of lin es sh ou ld be cou n ted ev en
th rou g h it is rg e iden t ified frequ en cy in th e same mod e. Th en , it is n ecessary to exa min e wh eth er th e preset
v a lu e for th e v ert ical dis play pos iti on o f It em 4-3 h as e xcee ded th e tot al n u mbe r of lin es. If e xcee ded, a
maximu m v alu e sh ou l d be set u p, wh ich does n ot exceed th e v ertical display pos ition of Ite m 4-3.
(2) Ou t-of -ran g e
Th is ou t-of-ra n g e mode is assu med wh en th e frequ en cy of th e h orizon ta l / v ertical sig n al is as sp ecified below.
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Vertical frequ en cy : Belo w 50Hz or a bov e 85Hz
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Horizon ta l fre qu en cy : Bel ow 24 KHz o r abo v e 75 KHz
(3) Power sav e mode
Th e power sa v e mode is assu med wh e n th e h orizon tal / v erti cal sig n als are as spec ified below.
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If th ere is n o h orizon tal sy n c sig n al in pu t.
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If th ere is n o v ertic al sy n c sig n al in pu t.
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If th e h o rizon tal sy n c sig n al is ou tside th e measu rin g ran g e of I300.
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If th e v e rtical sy n c sig n al is ou tside th e measu rin g ran g e of I300.
Ci rcu i t D escri p ti on
A L502
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