Q7. Figure 1 below shows the logic diagram of a real-time clock using six 4-bit counter modules, six BCD-to-7-segment decoder/drivers and six LED 7-segment displays. The 'hour', 'minute', and 'second' are each displayed using two 7-segment displays. [16]
CLK
MOD-2
(one FF)
BCD
counter
1 pulse/hr
MOD-6
counter
BCD
counter
1 pulse/min
MOD-6
counter
BCD
counter
Decoder/
display
0-9
Units
0-5
Tens
0-9
Units
"Minutes" section
Display
0-1
Tens
"Hours" section
Decoder/
display
0-5
Tens
Decoder/
display
0-9
Units
"Seconds" section
Figure 1
(a) For the "Tens" digit in the "Hours" section why is the counter configured as a MOD-2 counter?
(b) For the "Tens" digit in the "Minutes" and "Seconds" sections why are the counters configured as MOD-6 counters?
(c) Can you identify any errors in the clock input connections to the "Minutes" and "Hours" sections? If yes, how can you fix the connection errors?
(d) What is the frequency of the CLK signal required so that the system works as a REAL-TIME clock?
