COSMAC ELF 1802 Clock

I am exploring the idea of building a COSMAC ELF 1802 Clock.

This will be a clock based on the COSMAC ELF 1802 CPU along with some CMOS counters and a time base along with some kind of display.

The plan is that it will display time, date, and year. Since it is an "ELF clock" it will be describing the instant in time, defined as the number of days since the ELF was first described in Popular Electronic Magazine in August of 1976 (8/1/1976). This will be similar to Unix time but without the resolution down to a second.

The time keeping element would be a chain of 8 bit CMOS counters, one for seconds, minutes, and days. These counters could be read as input ports from the CPU.

For software I am trying Tiny Basic to see if it can at least update the display several times per minute. The display will not include seconds in the first revision if using Tiny Basic since it can not complete the calculation fast enough.

I have written the initial conversion of the day counter to calculate year, month, and day accounting for leap year. With a 1.75 Mhz clock speed using the Emma02 emulator it takes 20 seconds for the 300+ lines of code to complete the calculation. Since Tiny Basic only supports 16 bit integers the clock will have a limit of the year 2065.

Below is my code so far. I will remove the spaces after it is debugged to save space but for now it has only been slightly space compressed.

 5 PR "SERIAL EPOCH";  
 10 INPUT S  
 20 GOSUB 1000  
 30 GOSUB 3000  
 55 REM Y=YEAR L=LEAP TRUE/FALSE P=POSITION IN YEAR(DAYS) M=MONTH D=DAY  
 60 PR "14:23 ";M;"/";D;"/";Y  
 65 PR "Y=";Y;" L=";L;" P=";P;" M=";M;" D=";D  
 100 END  
 1000 IF S>0Y=1976  
 1005 IF Y=1976L=1  
 1007 IF Y=1976P=S-0  
 1010 IF S>153Y=1977  
 1015 IF Y=1977L=0  
 1017 IF Y=1977P=S-153  
 1020 IF S>518Y=1978  
 1025 IF Y=1978L=0  
 1027 IF Y=1978P=S-518  
 1030 IF S>883Y=1979  
 1035 IF Y=1979L=0  
 1037 IF Y=1979P=S-883  
 1040 IF S>1248Y=1980  
 1045 IF Y=1980L=1  
 1047 IF Y=1980P=S-1248  
 1050 IF S>1614Y=1981  
 1055 IF Y=1981L=0  
 1057 IF Y=1981P=S-1614  
 1060 IF S>1979Y=1982  
 1065 IF Y=1982L=0  
 1067 IF Y=1982P=S-1979  
 1070 IF S>2344Y=1983  
 1075 IF Y=1983L=0  
 1077 IF Y=1983P=S-2344  
 1080 IF S>2709Y=1984  
 1085 IF Y=1984L=1  
 1087 IF Y=1984P=S-2709  
 1090 IF S>3075Y=1985  
 1095 IF Y=1985L=0  
 1097 IF Y=1985P=S-3075  
 1100 IF S>3440Y=1986  
 1105 IF Y=1986L=0  
 1107 IF Y=1986P=S-3440  
 1110 IF S>3805Y=1987  
 1115 IF Y=1987L=0  
 1117 IF Y=1987P=S-3805  
 1120 IF S>4170Y=1988  
 1125 IF Y=1988L=1  
 1127 IF Y=1988P=S-4170  
 1130 IF S>4536Y=1989  
 1135 IF Y=1989L=0  
 1137 IF Y=1989P=S-4536  
 1140 IF S>4901Y=1990  
 1145 IF Y=1990L=0  
 1147 IF Y=1990P=S-4901  
 1150 IF S>5266Y=1991  
 1155 IF Y=1991L=0  
 1157 IF Y=1991P=S-5266  
 1160 IF S>5631Y=1992  
 1165 IF Y=1992L=1  
 1167 IF Y=1992P=S-5631  
 1170 IF S>5997Y=1993  
 1175 IF Y=1993L=0  
 1177 IF Y=1993P=S-5997  
 1180 IF S>6362Y=1994  
 1185 IF Y=1994L=0  
 1187 IF Y=1994P=S-6362  
 1190 IF S>6727Y=1995  
 1195 IF Y=1995L=0  
 1197 IF Y=1995P=S-6727  
 1200 IF S>7092Y=1996  
 1205 IF Y=1996L=1  
 1207 IF Y=1996P=S-7092  
 1210 IF S>7458Y=1997  
 1215 IF Y=1997L=0  
 1217 IF Y=1997P=S-7458  
 1220 IF S>7823Y=1998  
 1225 IF Y=1998L=0  
 1227 IF Y=1998P=S-7823  
 1230 IF S>8188Y=1999  
 1235 IF Y=1999L=0  
 1237 IF Y=1999P=S-8188  
 1240 IF S>8553Y=2000  
 1245 IF Y=2000L=1  
 1247 IF Y=2000P=S-8553  
 1250 IF S>8919Y=2001  
 1255 IF Y=2001L=0  
 1257 IF Y=2001P=S-8919  
 1260 IF S>9284Y=2002  
 1265 IF Y=2002L=0  
 1267 IF Y=2002P=S-9284  
 1270 IF S>9649Y=2003  
 1275 IF Y=2003L=0  
 1277 IF Y=2003P=S-9649  
 1280 IF S>10014Y=2004  
 1285 IF Y=2004L=1  
 1287 IF Y=2004P=S-10014  
 1290 IF S>10380Y=2005  
 1295 IF Y=2005L=0  
 1297 IF Y=2005P=S-10380  
 1300 IF S>10745Y=2006  
 1305 IF Y=2006L=0  
 1307 IF Y=2006P=S-10745  
 1310 IF S>11110Y=2007  
 1315 IF Y=2007L=0  
 1317 IF Y=2007P=S-11110  
 1320 IF S>11475Y=2008  
 1325 IF Y=2008L=1  
 1327 IF Y=2008P=S-11475  
 1330 IF S>11841Y=2009  
 1335 IF Y=2009L=0  
 1337 IF Y=2009P=S-11841  
 1340 IF S>12206Y=2010  
 1345 IF Y=2010L=0  
 1347 IF Y=2010P=S-12206  
 1350 IF S>12571Y=2011  
 1355 IF Y=2011L=0  
 1357 IF Y=2011P=S-12571  
 1360 IF S>12936Y=2012  
 1365 IF Y=2012L=1  
 1367 IF Y=2012P=S-12936  
 1370 IF S>13302Y=2013  
 1375 IF Y=2013L=0  
 1377 IF Y=2013P=S-13302  
 1380 IF S>13667Y=2014  
 1385 IF Y=2014L=0  
 1387 IF Y=2014P=S-13667  
 1390 IF S>14032Y=2015  
 1395 IF Y=2015L=0  
 1397 IF Y=2015P=S-14032  
 1400 IF S>14397Y=2016  
 1405 IF Y=2016L=1  
 1407 IF Y=2016P=S-14397  
 1410 IF S>14763Y=2017  
 1415 IF Y=2017L=0  
 1417 IF Y=2017P=S-14763  
 1420 IF S>15128Y=2018  
 1425 IF Y=2018L=0  
 1427 IF Y=2018P=S-15128  
 1430 IF S>15493Y=2019  
 1435 IF Y=2019L=0  
 1437 IF Y=2019P=S-15493  
 1440 IF S>15858Y=2020  
 1445 IF Y=2020L=1  
 1447 IF Y=2020P=S-15858  
 1450 IF S>16224Y=2021  
 1455 IF Y=2021L=0  
 1457 IF Y=2021P=S-16224  
 1460 IF S>16589Y=2022  
 1465 IF Y=2022L=0  
 1467 IF Y=2022P=S-16589  
 1470 IF S>16954Y=2023  
 1475 IF Y=2023L=0  
 1477 IF Y=2023P=S-16954  
 1480 IF S>17319Y=2024  
 1485 IF Y=2024L=1  
 1487 IF Y=2024P=S-17319  
 1490 IF S>17685Y=2025  
 1495 IF Y=2025L=0  
 1497 IF Y=2025P=S-17685  
 1500 IF S>18050Y=2026  
 1505 IF Y=2026L=0  
 1507 IF Y=2026P=S-18050  
 1510 IF S>18415Y=2027  
 1515 IF Y=2027L=0  
 1517 IF Y=2027P=S-18415  
 1520 IF S>18780Y=2028  
 1525 IF Y=2028L=1  
 1527 IF Y=2028P=S-18780  
 1530 IF S>19146Y=2029  
 1535 IF Y=2029L=0  
 1537 IF Y=2029P=S-19146  
 1540 IF S>19511Y=2030  
 1545 IF Y=2030L=0  
 1547 IF Y=2030P=S-19511  
 1550 IF S>19876Y=2031  
 1555 IF Y=2031L=0  
 1557 IF Y=2031P=S-19876  
 1560 IF S>20241Y=2032  
 1565 IF Y=2032L=1  
 1567 IF Y=2032P=S-20241  
 1570 IF S>20607Y=2033  
 1575 IF Y=2033L=0  
 1577 IF Y=2033P=S-20607  
 1580 IF S>20972Y=2034  
 1585 IF Y=2034L=0  
 1587 IF Y=2034P=S-20972  
 1590 IF S>21337Y=2035  
 1595 IF Y=2035L=0  
 1597 IF Y=2035P=S-21337  
 1600 IF S>21702Y=2036  
 1605 IF Y=2036L=1  
 1607 IF Y=2036P=S-21702  
 1610 IF S>22068Y=2037  
 1615 IF Y=2037L=0  
 1617 IF Y=2037P=S-22068  
 1620 IF S>22433Y=2038  
 1625 IF Y=2038L=0  
 1627 IF Y=2038P=S-22433  
 1630 IF S>22798Y=2039  
 1635 IF Y=2039L=0  
 1637 IF Y=2039P=S-22798  
 1640 IF S>23163Y=2040  
 1645 IF Y=2040L=1  
 1647 IF Y=2040P=S-23163  
 1650 IF S>23529Y=2041  
 1655 IF Y=2041L=0  
 1657 IF Y=2041P=S-23529  
 1660 IF S>23894Y=2042  
 1665 IF Y=2042L=0  
 1667 IF Y=2042P=S-23894  
 1670 IF S>24259Y=2043  
 1675 IF Y=2043L=0  
 1677 IF Y=2043P=S-24259  
 1680 IF S>24624Y=2044  
 1685 IF Y=2044L=1  
 1687 IF Y=2044P=S-24624  
 1690 IF S>24990Y=2045  
 1695 IF Y=2045L=0  
 1697 IF Y=2045P=S-24990  
 1700 IF S>25355Y=2046  
 1705 IF Y=2046L=0  
 1707 IF Y=2046P=S-25355  
 1710 IF S>25720Y=2047  
 1715 IF Y=2047L=0  
 1717 IF Y=2047P=S-25720  
 1720 IF S>26085Y=2048  
 1725 IF Y=2048L=1  
 1727 IF Y=2048P=S-26085  
 1730 IF S>26451Y=2049  
 1735 IF Y=2049L=0  
 1737 IF Y=2049P=S-26451  
 1740 IF S>26816Y=2050  
 1745 IF Y=2050L=0  
 1747 IF Y=2050P=S-26816  
 1750 IF S>27181Y=2051  
 1755 IF Y=2051L=0  
 1757 IF Y=2051P=S-27181  
 1760 IF S>27546Y=2052  
 1765 IF Y=2052L=1  
 1767 IF Y=2052P=S-27546  
 1770 IF S>27912Y=2053  
 1775 IF Y=2053L=0  
 1777 IF Y=2053P=S-27912  
 1780 IF S>28277Y=2054  
 1785 IF Y=2054L=0  
 1787 IF Y=2054P=S-28277  
 1790 IF S>28642Y=2055  
 1795 IF Y=2055L=0  
 1797 IF Y=2055P=S-28642  
 1800 IF S>29007Y=2056  
 1805 IF Y=2056L=1  
 1807 IF Y=2056P=S-29007  
 1810 IF S>29373Y=2057  
 1815 IF Y=2057L=0  
 1817 IF Y=2057P=S-29373  
 1820 IF S>29738Y=2058  
 1825 IF Y=2058L=0  
 1827 IF Y=2058P=S-29738  
 1830 IF S>30103Y=2059  
 1835 IF Y=2059L=0  
 1837 IF Y=2059P=S-30103  
 1840 IF S>30468Y=2060  
 1845 IF Y=2060L=1  
 1847 IF Y=2060P=S-30468  
 1850 IF S>30834Y=2061  
 1855 IF Y=2061L=0  
 1857 IF Y=2061P=S-30834  
 1860 IF S>31199Y=2062  
 1865 IF Y=2062L=0  
 1867 IF Y=2062P=S-31199  
 1870 IF S>31564Y=2063  
 1875 IF Y=2063L=0  
 1877 IF Y=2063P=S-31564  
 1880 IF S>31929Y=2064  
 1885 IF Y=2064L=1  
 1887 IF Y=2064P=S-31929  
 1890 IF S>32295Y=2065  
 1895 IF Y=2065L=0  
 1897 IF Y=2065P=S-32295  
 2000 RETURN  
 3000 IF Y=1976 L=3  
 3010 IF L=0 GOSUB 4000  
 3020 IF L=1 GOSUB 5000  
 3030 IF L=3 GOSUB 6000  
 3040 RETURN  
 4000 IF P>0M=1  
 4010 IF P>0D=P  
 4020 IF P>31M=2  
 4030 IF P>31D=P-31  
 4040 IF P>59M=3  
 4050 IF P>59D=P-59  
 4060 IF P>90M=4  
 4070 IF P>90D=P-90  
 4080 IF P>120M=5  
 4090 IF P>120D=P-120  
 4100 IF P>151M=6  
 4110 IF P>151D=P-151  
 4120 IF P>181M=7  
 4130 IF P>181D=P-181  
 4140 IF P>212M=8  
 4150 IF P>212D=P-212  
 4160 IF P>243M=9  
 4170 IF P>243D=P-243  
 4180 IF P>273M=10  
 4190 IF P>273D=P-273  
 4200 IF P>304M=11  
 4210 IF P>304D=P-304  
 4220 IF P>334M=12  
 4230 IF P>334D=P-334  
 4900 RETURN  
 5000 IF P>0M=1  
 5010 IF P>0D=P  
 5020 IF P>31M=2  
 5030 IF P>31D=P-31  
 5040 IF P>60M=3  
 5050 IF P>60D=P-60  
 5060 IF P>91M=4  
 5070 IF P>91D=P-91  
 5080 IF P>121M=5  
 5090 IF P>121D=P-121  
 5100 IF P>152M=6  
 5110 IF P>152D=P-152  
 5120 IF P>182M=7  
 5130 IF P>182D=P-182  
 5140 IF P>213M=8  
 5150 IF P>213D=P-213  
 5160 IF P>244M=9  
 5170 IF P>244D=P-244  
 5180 IF P>274M=10  
 5190 IF P>274D=P-274  
 5200 IF P>305M=11  
 5210 IF P>305D=P-305  
 5220 IF P>335M=12  
 5230 IF P>335D=P-335  
 5240 RETURN  
 6000 RETURN  
 0  

Running 40 year old software

It is amazing to be able to run software (code) that is 40 years old. I was able to run code that I have not run since I was a kid in 1978 on my then recently built Netronics ELF kit.

I have mentioned this emulator before --> http://www.elf-emulation.com/ but recently decided to try to get it to run the PIXIE code the was published in Popular Electronic July 1977 issue. The emulator for the COSMAC 1802 CPU can also emulate the CDP1861 PIXIE video chip too. I used the original articles code and created a rom file and loaded it in the emulator and it worked! Below is the image generated and what was display on the TV of the original ELF. The random looking blocks at the top of the image are actually the code that is running to display the image. The PIXIE chip is displaying 256 bytes of memory arranged 8 bytes wide by 32 bytes high, with each spot or pixel being 1 bit. Hence a 64 pixel by 256 pixel image. The ELF only had 256 bytes of memory. If you had more memory you could assign a specific memory space just for the video image and another for the code.

elf.exe -r pixie.rom -a -1861

I remember keying that code into the ELF II above via the hex keypad and being totally amazed when I saw it on my TV I had connected. I then later devised my only images to be displayed.