INT 15 - Amstrad PC1512 - WRITE DATA TO NON-VOLATILE RAM
AH = 01h
AL = NVRAM location (00h to 3Fh)
BL = NVRAM data value
Return: AH = return code
00h OK
01h address bad
02h write error

Format of NVRAM:
Offset  Size    Description
00h    BYTE    time of day: seconds
01h    BYTE    alarm time: seconds
02h    BYTE    time of day: minutes
03h    BYTE    alarm time: minutes
04h    BYTE    time of day: hours
05h    BYTE    alarm time: hours
06h    BYTE    day of week, 1 = Sunday
07h    BYTE    day of month
08h    BYTE    month
09h    BYTE    year mod 100
0Ah    BYTE    RTC status register A
bit 7: set if date/time being updated
6-4: time base speed, default 010 = 32768 Hz
3-0: interrupt rate selection, default 0110 = 1024 Hz
0Bh    BYTE    RTC status register B
bit 7: clear if normal update, set if abort update
6: periodic interrupt enable
5: alarm interrupt enable
4: update end interrupt enable
3: square wave enable
2: date mode (clear = BCD, set = binary)
1: 24-hour format
0: daylight saving time enable
0Ch    BYTE    RTC status register C (read-only)
bit 7: IRQF flag
6: PF flag
5: AF flag
4: UF flag
0Dh    BYTE    RTC status register D
bit 7: battery good
0Eh  6 BYTEs   time and date machine last used
14h    BYTE    user RAM checksum
15h    WORD    Enter key scancode/ASCII code
17h    WORD    Forward delete key scancode/ASCII code
19h    WORD    Joystick fire button 1 scancode/ASCII code
1Bh    WORD    Joystick fire button 2 scancode/ASCII code
1Dh    WORD    mouse button 1 scancode/ASCII code
1Fh    WORD    mouse button 2 scancode/ASCII code
21h    BYTE    mouse X scaling factor
22h    BYTE    mouse Y scaling factor
23h    BYTE    initial VDU mode and drive count
24h    BYTE    initial VDU character attribute
25h    BYTE    size of RAM disk in 2K blocks
26h    BYTE    initial system UART setup byte
27h    BYTE    initial external UART setup byte
28h 24 BYTEs   available for user application
Note:   bytes 00h-0Dh are the same on the IBM AT as they are used/updated by
the clock chip

See also: 1502

1501 - Amstrad PC1512 - WRITE DATA TO NON-VOLATILE RAM