The source code below combines pieces from Dallas 1302 RTC and Dallas 1621 temperature sensor experiments to create a simple temperature logger application:

MTOP=05FFFH 10 REM data logger v1 20 GOSUB 1900:GOSUB 2000 30 GOSUB 1900:LM=MI 100 GOSUB 1900:IF LM=MI THEN GOTO 100 110 LM=MI 120 GOSUB 2100 150 GOSUB 800 151 PRINT ",", 170 print T 190 GOTO 100 799 END 800 REM print formatted time 810 X=D : GOSUB 900 : PRINT "/", 812 X=M : GOSUB 900 : PRINT "/20", 814 X=Y : GOSUB 900 : PRINT ",", 820 X=H : GOSUB 900 : PRINT ":", 822 X=MI : GOSUB 900 : PRINT ":", 825 X=S : GOSUB 900 830 RETURN 900 REM print pure BCD 905 X=X.AND.255 910 Z=INT(X/16) 915 GOSUB 930 920 Z=X.AND.15 930 IF Z>9 THEN Z=Z+7 940 Z=Z+48 : PRINT CHR(Z), 950 RETURN 1000 REM lines 1000-2000 contain Dallas 1302 RTC support 1005 REM send CMD as command 1030 FOR I=1 TO 8 : CN=CMD.AND.1 : CMD=CMD/2 1050 PORT1=0FCH.OR.CN : PORT1=0FEH.OR.CN : PORT1=0FCH.OR.CN 1090 NEXT : PORT1=0FDH : RETURN 1100 REM Pull RST low 1102 PORT1=0FDH : PORT1=0BDH : RETURN 1200 REM pull clock low, RST high 1210 PORT1=0BDH : PORT1=0FDH : RETURN 1300 REM Read first byte after command to CMD 1328 CMD=0 : FOR I=1 TO 7 : CN=PORT1.AND.1 1340 CMD=CMD/2 : CMD=CN*128+CMD 1360 PORT1=0FFH : PORT1=0FDH : NEXT 1381 CN=PORT1.AND.1 : CMD=CMD/2 : CMD=CN*128+CMD 1390 RETURN 1400 REM Read next byte in burst to CMD 1410 PORT1=0FFH : PORT1=0FDH : GOTO 1300 1500 REM start charging 1505 GOSUB 1600 : GOSUB 1200 : CMD=090H : GOSUB 1000 1520 CMD=0A5H : GOSUB 1000 : GOSUB 1100 : GOSUB 1700 : RETURN 1600 REM enable writing to clock 1610 GOSUB 1200 : CMD=08EH : GOSUB 1000 : CMD=0 : GOSUB 1000 1630 GOSUB 1100 : RETURN 1700 REM disable writing to clock 1710 GOSUB 1200 : CMD=08EH : GOSUB 1000 : CMD=080H : GOSUB 1000 1730 GOSUB 1100 : RETURN 1800 REM change time 1810 Y=001H 1811 M=003H 1812 D=031H 1813 H=022H 1814 MI=030H 1815 S=000H 1816 W=6 1825 GOSUB 1600 : GOSUB 1200 1830 CMD=0BEH : GOSUB 1000 : CMD=S : GOSUB 1000 1832 CMD=MI : GOSUB 1000 : CMD=H : GOSUB 1000 1834 CMD=D : GOSUB 1000 : CMD=M : GOSUB 1000 1836 CMD=W : GOSUB 1000 : CMD=Y : GOSUB 1000 1838 CMD=0 : GOSUB 1000 : GOSUB 1100 1860 GOSUB 1700 : RETURN 1900 REM read date/time to vars 1910 GOSUB 1200 : CMD=0BFH : GOSUB 1000 1930 GOSUB 1300 : S=CMD : GOSUB 1400 : MI=CMD 1932 GOSUB 1400 : H=CMD : GOSUB 1400 : D=CMD 1934 GOSUB 1400 : M=CMD : GOSUB 1400 : W=CMD 1936 GOSUB 1400 : Y=CMD : GOSUB 1400 : GOSUB 1100 : RETURN 2000 REM lines 2000-3000 contain Dallas 1621 temp sensor support 2010 REM initialize sensor interface 2011 REM build PORT3 access functions 2012 XBY(6000H)=085H : XBY(6001H)=0B0H : XBY(6002H)=020H : XBY(6003H)=022H 2013 XBY(6004H)=085H : XBY(6005H)=020H : XBY(6006H)=0B0H : XBY(6007H)=022H 2015 REM do the interface init 2020 GOSUB 2200: GOSUB 2300 2025 BY=090H : GOSUB 2600 : BY=0EEH : GOSUB 2600 : GOSUB 2400 2028 RETURN 2100 REM read the temperature to T and return 2110 GOSUB 2200 : GOSUB 2300: BY=090H : GOSUB 2600 2136 BY=0AAH : GOSUB 2600 2144 GOSUB 2400 2146 GOSUB 2300 2150 BY=091H : GOSUB 2600 2160 GOSUB 2700 : GOSUB 2800 2165 BH=BY 2166 GOSUB 2700 : GOSUB 2900: GOSUB 2400 2190 T=BH*256+BY: T=T/256:return 2200 REM idle 2210 DBY(20H)=255 : CALL 6004H : RETURN 2300 REM start 2310 DBY(20H)=0EFH : CALL 6004H : DBY(20H)=0CFH : CALL 6004H : RETURN 2400 REM stop 2410 DBY(20H)=0CFH : CALL 6004H : DBY(20H)=0EFH : CALL 6004H 2415 DBY(20H)=0FFH : CALL 6004H : RETURN 2500 REM get ack 2510 DBY(20H)=0CFH : CALL 6004H : DBY(20H)=0DFH : CALL 6004H 2530 DBY(20H)=0FFH : CALL 6004H : CALL 6000H 2540 A=DBY(20H).AND.16 : DBY(20H)=0DFH : CALL 6004H 2550 DBY(20H)=0CFH : CALL 6004H : RETURN 2600 REM send BY, get ack to A 2610 FOR I=1 TO 8 : BT=BY.AND.128 : BY=BY+BY : BT=BT/8 2640 DBY(20H)=0CFH.OR.BT : CALL 6004H : DBY(20H)=0EFH.OR.BT : CALL 6004H 2660 DBY(20H)=0CFH.OR.BT : CALL 6004H : NEXT I : GOSUB 2500 : RETURN 2700 REM read BY 2710 BY=0 : DBY(20H)=0DFH : CALL 6004H 2720 FOR I=1 TO 8 : DBY(20H)=0FFH : CALL 6004H 2740 CALL 6000H : BT=DBY(20H).AND.16 2745 DBY(20H)=0DFH : CALL 6004H : BT=BT/16 : BY=BY+BY+BT 2770 NEXT I : RETURN 2800 REM send ACK 2810 DBY(20H)=0CFH : CALL 6004H : DBY(20H)=0EFH : CALL 6004H 2820 DBY(20H)=0CFH : CALL 6004H : RETURN 2900 REM send NAK 2910 DBY(20H)=0DFH : CALL 6004H : DBY(20H)=0FFH : CALL 6004H 2920 DBY(20H)=0DFH : CALL 6004H : RETURN

The data logger outputs a timestamped temperature reading once every minute, in a format DD/MM/YYYY,HH:MM:SS, TT.T where TT.T is temperature reading. As BASIC-52 does not have an internal function to output BCD numbers without 'H' added to it, there is a subroutine at line 900 which outputs a two-digit BCD number from a number contained in variable X. Subroutine at line 800 then uses it to output the current date and time. Temperature is output by using a built-in PRINT and thus it has spaces around it.

If you change line 100 to read just

100 GOSUB 1900

then you will get contignous temperature readings. I used this change to track the temperature change speed, captured the output to file, opened it in Excel, and made a chart:

I used an icecube in plastic bag to cool the chip down to +6 degC, then let it raise to room temperature of +27 degC. As you can see, the process took about 13 minutes - DS1621 is not a very fast responding device.