Sharp CE-150 - Page 255

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2-3. Functions
14
2-3-1. Timer
Th e ti ntt cr is a 9- bit poly norn inal co un te r. ·rhc cou nter va lu e c an be set by t he AMO or
AM I instructi on of the CPU. Shown in .. POLI NO MINAI. CO UN'rE R .. is th e li st o f
h cxadcc in 1al data of cou nter \v ith d cc in1 al count nurnb cr .
TI1e t i1 ner ope rat es co nt in uo us ly at a lJ ti rn c s. \\ ih cn the co un te r va l ue reach es 11 =- i-:H. it
i ssues interrupt reque st to t he CPU. If IE ( lnt cn upt E nable) fl ag is ac ti ve at that poim. the
Cl)U j u n1ps to t he t in 1cr in t errupt pro ce ss in g ro utine \vh os c high order byte addre ss is
represented by the contents of the addr ess F FFAH a nd l ow order b y1c addr ess by the
co nt en ts of the ad dre ss FFFl3H. TI 1c tim er has 10 be set to OOO H when it is not used.
S in ce it cou n ts in sync hroni 1; · 11 ion \Vith th e cl oc k <l>F . eac h one c ycle or <J> F in cr~ nt c n ts th e
co unter one st ep.
L. __ D_iv_id_ ,e _r _ _,I - <I> F
\Vhen chc 4rvtH z cr ys ta l os cillator is in co n nec tio n. th e ti n1e r is incre n1 en ted at C(lch
32µscc. because <PF is 3 I .25k Hz.
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