[RESOLVED] Date and Time functions print wrong results?

[David2010]

This is a strange one.

The functions print "something" without error however the results are wrong. Generally speaking, with me the whole function don't work. xD

These two functions get the time and date from the BIOS and print it to the screen.

Date:

date: 

	%define RTCaddress	0x70
	%define RTCdata		0x71
	
loop3:	mov al,10			;Get RTC register A
	out RTCaddress,al
	in al,RTCdata
	test al,0x80			;Is update in progress?
	jne loop3				; yes, wait
	
	mov al,0x07			;Get day
	out RTCaddress,al
	in al,RTCdata
	mov [RTCtimeDay],al

	mov al,0x08			;Get month
	out RTCaddress,al
	in al,RTCdata
	mov [RTCtimeMonth],al
	
	mov al,0x09			;Get year
	out RTCaddress,al
	in al,RTCdata
	mov [RTCtimeYear],al
	
	mov si, msg3
    call print
    
    mov si, [RTCtimeMonth]
    call printints
    
    mov si, msg1
    call print    
	
	mov si, [RTCtimeDay]
    call printints
    
    mov si, msg1
    call print

    mov si, [RTCtimeYear]
    call printints
    
    mov si, msg2
    call print
   
ret

msg1 db '    ', 0
msg2 db ' ', 0x0D, 0x0A, 0
msg3 db 'Month Day Year', 0x0D, 0x0A, 0
RTCtimeDay db 0, 0   
RTCtimeMonth db 0, 0
RTCtimeYear db 0, 0

Time:

time: 

	%define RTCaddress	0x70
	%define RTCdata		0x71
	
loop1:	mov al,10			;Get RTC register A
	out RTCaddress,al
	in al,RTCdata
	test al,0x80			;Is update in progress?
	jne loop1				; yes, wait
	
	mov al,0x04			;Get hours 
	out RTCaddress,al
	in al,RTCdata
	mov [RTCtimeHour],al	

	mov al,0x02			;Get minutes 
	out RTCaddress,al
	in al,RTCdata
	mov [RTCtimeMinute],al

	mov si, [RTCtimeHour]
    call printints
    
    mov si, msg_hours
    call print

    mov si, [RTCtimeMinute]
    call printints
    
    mov si, msg_minutes
    call print
   
ret

msg_minutes db ' Minutes', 0x0D, 0x0A, 0
msg_hours db ' Hours ', 0
RTCtimeHour db 0, 0   
RTCtimeMinute db 0, 0

The problem is, the data printed by these two functions are wrong.

I already checked the BIOS and made sure the date and time values were correct there.

--------------------------------------------

Register values after each function:

---------------------------------------------

Time function:

ax = 31704
cx = 64
dx = 1
bx = 40
si = 40
di = 0

Date function:

ax = 31704
cx = 64
dx = 1
bx = 44
si = 44
di = 0

[Eri523]

These two functions get the time and date from the BIOS [...].

Well, they don't get the date/time from the BIOS, but rather directly from the RTC hardware. (However, there are BIOS functions to access the RTC: INT 0x1A, function 0x02 and up.)

Your problem most likely arises from the fact that the RTC usually is configured to deliver (and receive) the date/time values in BCD rather than binary (bit 2 of status register B is 0), but you interpret them as being binary (assuming that you use the integer output routine from our other thread).

BTW, the BIOS functions for accessing the RTC I mentioned above use the BCD format as well.

HTH

[David2010]

Well, they don't get the date/time from the BIOS, but rather directly from the RTC hardware. (However, there are BIOS functions to access the RTC: INT 0x1A, function 0x02 and up.)

Your problem most likely arises from the fact that the RTC usually is configured to deliver (and receive) the date/time values in BCD rather than binary (bit 2 of status register B is 0), but you interpret them as being binary (assuming that you use the integer output routine from our other thread).

BTW, the BIOS functions for accessing the RTC I mentioned above use the BCD format as well.

HTH

This small function converts from BCD to binary.

Thank you again for your help!

bcd2int:
    mov ah,al
    shr ah,4
    and al,0x0F
    aad
    or al,ah
    ret