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Download M68HC05 Applications Guide
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Freescale Semiconductor, Inc. Applications Listing — Thermostat Example Sheet 13 of 21 Freescale Semiconductor, Inc... ************************************************************** * HVAC — Update Fan, Heat, and Cool outputs * * Low-true outputs will be buffered to drive 24VAC * * relay coils in HVAC equipment.(high true in final) * * Heat and Cool requests should not permit short* * cycle (ie a min delay is required between changes) * * Once Heat or Cool requested, do not turn off for * * at least 30 sec. Also enforce 30 sec. minimum * * off time to restart. * * Allow ± 1° around target temp as hysteresis. * * HVACM = 0 — Off, 1 — Heat, 2 — Cool, 3 — Fan Only * ************************************************************** 0334 0334 0336 0338 033a 033c 033e 0340 0342 0344 0346 0348 034a 034c 034e 0350 b6 27 al 26 b6 26 b6 aa b7 20 a1 26 1a b6 0c 0353 0354 0356 0358 035a 035c 035e 4c b1 24 Ic le 3f 20 0360 0361 0363 0365 0367 0369 036b 036d 036f 0371 0373 0375 0377 0379 037b 037d 037f 4a bl 23 lf ld a6 b7 20 a1 27 1f 1c la 20 lc b6 0a HVAC EQU Update Fan, Heat, and Cool outputs a3 LDA SEC Exit unless sec = 0 or 30 04 BEQ DOHVAC 0 so do HVAC le CMP #30 60 BNE XHVAC Exit if not 0 or 30 aa DOHVAC LDA HVACM 0-off, 1-heat, 2-cool, 3-fan 08 BNE HM1Q If not 0 go see if 1 02 LDA PORTC Fan*,Heat*,Cool*,Beep;ADen*,E,RS,R/W e0 ORA #$EO Set fan, heat, cool all high (off) 02 STA PORTC Update port 54 BRA XHVAC & Exit 01 HM1Q CMP #1 Check for mode 1-heat 23 BNE HM2Q If not go see if 2 02 BSET 5rPORTC Turn off cool output ab LDA GOAL Get target temp 02 0d BRSET 6,PORTC,HONQ If not; see if it should be * Heat on; turn off when indoor temp > goal + 1 INCA Goal + 1 for hysteresis ac CMP INTMP GOAL + 1 < INTMP ? Turn off ? 44 BHS XHVAC NO; just leave 02 BSET 6,PORTC Turn off heat 02 BSET 7,PORTC Turn off fan b2 CLR HVACON Turn off flag to indicate off 3c BRA XHVAC Then leave * Heat off; turn on when indoor temp < goal-1 HONQ DECA Goal-1 for hysteresis ac CMP INTMP GOAL-1 > INTMP ? Turn on ? 37 BLS XHVAC NO; just leave 02 BCLR 7,PORTC Turn on fan 02 BCLR 6,PORTC Turn on heat 01 LDA #1 b2 STA HVACON Set flag to indicate on 2d BRA XHVAC Then leave 02 HM2Q CMP #2 Check for mode 2-cool 08 BEQ HCOOL Branch if cool mode 2 02 BCLR 7,PORTC Turn on fan 02 BSET 6,PORTC Turn off heat 02 BSET 5,PORTC Turn off cool 21 BRA XHVAC Then leave 02 HCOOL BSET 6,PORTC Turn off heat output ab LDA GOAL Get target temp 02 0d BRSET 5,PORTC,CONQ If not; see if it should be M68HC05 Applications Guide — Rev. 4.0 224 Applications For More Information On This Product, Go to: www.freescale.com MOTOROLA
