I am using AT89S52 along with DS1307 RTC for a clock project.Everything is fine,except for the minutes and hours display.40 minutes is shown as '00',41 as 01....59 as 19 and then it rolls back to usual 00. Any minute value greater than 40 when written to the clock,results in a display as mentioned above.

24 hour format is being used. Only 00,04,08,10,14,18,20 are shown...as like, for any hour value between 00 and 03,00 is shown.Similarly for 04-07 there is only 04 on the display.Though it is noteworthy that whenever the hours register value increments while the clock is running, the display shows it correctly.That means writing any value other than the 7 values mentioned above to the hours register, results in display of value no other than the 7 values.but while the clock register updates as it ticks, the display is as it should be. I don't understand where does the problem lie within.Is it plausible,that the reason to such a glitch can be attributed to corruption of RTC internal registers?