SECTION 6
Conversions and Interfaces
PEN*KEY
R
6200/6300 Hand-Held Computer Programmer’s Reference Guide 6-113
Timer and Real-Time Clock Services: INT 1Ah
Functions not supported return with the carry flag set. The carry flag is also set
if the realĆtime clock is not operational. Individual functions are selected by the
content of the AH register when INT 1Ah is invoked.
INT 1Ah, Function AH = 00h: Read System Timer Ticks
BIOS
Retrieves the values from the BIOS data areas 40:6Eh (high word) and 40:6Ch
(low word). The value returned is the total number of clock ticks since midnight
of system timer channel 0. Clock ticks occur 18.2 times per second and are
processed by INT 08h. Interrupts are disabled while the timer tick is read to
prevent update during access to the memory locations. The timer overflow flag,
returned in AL, is reset to zero when this function is executed.
On Entry:
AH = 00h
On Return:
CX = High word of system timer tick count
DX = Low word of system timer tick count
AL = Timer overflow flag
0 if day has not rolled over since last read
1 if timer value has exceeded 24 hours
INT 1Ah, Function AH = 01h: Set System Timer Ticks
BIOS
Sets the BIOS data values located at 40:6Ch and 40:6Eh to the data contained in
CX and DX, respectively. It thereby sets the system timer tick count. Execution
of this function clears the timer overflow flag at location 40:70h.
On Entry:
AH = 01h
CX = High byte of the system timer tick count
DX = Low byte of the system timer tick count
On Return:
None
6. Conversions and
Interfaces
