real time clock

[sayzer]

....
for am 12 hr mode
writehour = 00100011 = $C4
readhour = 10100011 = $A3

for pm 12 hr mode
readhour = 10101011 = $AB
writehour = 00101011 = $D4

hi jessey,

When reading or writing you change the register address command.

Reading: $85
Writing : $84

If you want to "Write Hour" to the chip, then you first send $84 command and prepare the chip to accept the incoming data for "hour". Then right after that you send your byte variable consisting your "hour data".

If sending 12Hr AM mode then the Bit7 of your byte should be "0" indicating 12Hr mode, and Bit5 should be "1 " indicating "AM".

Sending $85 command to the chip will be for "read hour" command and incoming data byte will consist of "hour data". Thus for reading, you do not set a byte to write to the chip; just read the incoming data.

In this case, I need to correct your arrangement as below.

12AM hr mode
writehour = 00100011
Bit7=0 12hr mode.
Bit5=1 AM mode.
Correct

readhour = 10100011
No need.
Just send $85 and read the incoming data.


12PM hr mode
writehour = 00101011
Bit7=0 12hr mode.
bit5=1 AM mode.
incorrect

The correct byte arrangement:
writehour = 00001011
Bit7=0 12Hr mode.
bit5=0 PM mode.


readhour = 10101011
No need.
Just send $85 and read the incoming data.

I have another question for you if you understand Melanie's ConvertBCD: subroutine above, what does the DIG 1 & DIG 0 do?

In a byte or word, the digits counts from right to left (just like Arabic).

Say we have a byte and it is set to Decimal 245.

ex:
Test VAR BYTE
Apple VAR BYTE

Test = 245

In this case, from right to left,
Test Dig 0 is 5
Test Dig 1 is 4
Test Dig 2 is 2

to extract any of these numbers and use in somewhere else, we use;

Apple = Test Dig 1

Apple is now 4.



How is it now ?
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