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2151 EE2E 4E 2A A4 LSR CPIY ;MAKE ROOM FOR MSB
2152 EE31 0D 2A A4 ORA CPIY ;OR IN SIGN BIT
2153 EE34 8D 2A A4 STA CPIY ;REPLACE CHAR
2154 EE37 88 DEY
2155 EE38 D0 F1 BNE GETA1
2156 EE3A 60 RTS
2157 EE3B ;GET ONE BIT FROM TAPE AND
2158 EE3B ;RETURN IT IN SIGN OF A (MSB)
2159 EE3B AD 08 A4 RDBIT LDA TSPEED ;ARE WE IN C7 OR 5B,5A FREQUENC`
2160 EE3E 30 27 BMI RDBIT4 ;JUMP TO C7 FREQ FORMAT
2161 EE40 20 75 EE JSR CKFREQ ;START BIT IN HIGH FREQ
2162 EE43 20 75 EE RDBIT1 JSR CKFREQ ;HIGH TO LOW FREQ TRANS
2163 EE46 B0 FB BCS RDBIT1
2164 EE48 AD 96 A4 LDA DIV64 ;GET HIGH FREQ TIMING
2165 EE4B 48 PHA
2166 EE4C A9 FF LDA #$FF ;SET UP TIMER
2167 EE4E 8D 96 A4 STA DIV64
2168 EE51 20 75 EE RDBIT2 JSR CKFREQ ;LOW TO HIGH FREQ TRANS
2169 EE54 90 FB BCC RDBIT2 ;WAIT TILL FREQ IS HIGH
2170 EE56 68 PLA
2171 EE57 38 SEC
2172 EE58 ED 96 A4 SBC DIV64 ;(256-T1) - (256-T2) =T2-T1
2173 EE5B 48 PHA ;LOW FREQ TIME-HIGH FREQ TIME
2174 EE5C A9 FF LDA #$FF
2175 EE5E 8D 96 A4 STA DIV64 ;SET UP TIMER
2176 EE61 68 PLA
2177 EE62 49 FF EOR #$FF
2178 EE64 29 80 AND #$80
2179 EE66 60 RTS
2180 EE67 ;EACH BIT STARTS WITH HALF PULSE OF 2400 & THEN
2181 EE67 ;3 HALF PULSES OF 1200 HZ FOR 0 ,3 PUSLES OF 2400 FOR 1
2182 EE67 ;THE READING IS MADE ON THE FOURTH 1/2 PULSE ,WHERE
2183 EE67 ;THE SIGNAL HAS STABILIZED
2184 EE67 20 75 EE RDBIT4 JSR CKFREQ ;SEE WHICH FREQ
2185 EE6A 90 FB BCC RDBIT4
2186 EE6C 20 75 EE JSR CKFREQ
2187 EE6F 20 75 EE JSR CKFREQ
2188 EE72 4C B5 FF JMP PATC24 ;NOW READ THE BIT
2189 EE75
2190 EE75 2C 00 A8 CKFREQ BIT DRB ;ARE WE HIGH OR LOW ?
2191 EE78 30 27 BMI CKF4
2192 EE7A 2C 00 A8 CKF1 BIT DRB ;WAIT TILL HIGH
2193 EE7D 10 FB BPL CKF1
2194 EE7F 65 00 ADC $00 ;EQUALIZER
2195 EE81 AD 09 A8 CKF2 LDA T2H ;SAVE CNTR
2196 EE84 48 PHA
2197 EE85 AD 08 A8 LDA T2L
2198 EE88 48 PHA
2199 EE89 A9 FF LDA #$FF
2200 EE8B 8D 09 A8 STA T2H ;START CNTR
2201 EE8E AD 08 A4 LDA TSPEED
2202 EE91 30 06 BMI CKF3 ;SUPER SPEED ?
2203 EE93 68 PLA
2204 EE94 CD 08 A4 CMP TSPEED ;HIGH OR LOW FREC
2205 EE97 68 PLA ;C=1 IF HIGH ,C=0 IF LOW
2206 EE98 60 RTS
2207 EE99 68 CKF3 PLA
2208 EE9A CD 08 A4 CMP TSPEED ;CENTER FREQ
2209 EE9D 68 CKF3A PLA
2210 EE9E E9 FE SBC #$FE
2211 EEA0 60 RTS
2212 EEA1 2C 00 A8 CKF4 BIT DRB ;WAIT TILL LOW