Programmable Timer Interrupt; M-Bus Interrupts - Motorola MC68HC05T16 Technical Data Manual

4.2.4

Programmable Timer Interrupt

Four timer interrupt flags are found in the top nibble of the Timer Status register (TSR) at location
$11. All four interrupts will vector to the same address at location $FFF6-$FFF7.
Each flag bit is defined as follows:
4
Timer Status Register
TOF - Timer Overflow Flag
OC0F, OC1F - Output Compare Flag 1 and Output Compare 2
ICF - Input Capture Flag
All four timer interrupt flags have corresponding enable bits (ICIE, OC0IE, OC1IE, and TOIE)
found in the Timer Control register (TCR) at location $10. Reset clears all enable bits preventing
an interrupt from occurring. The actual processor interrupt is generated only if the interrupt mask
bit of the condition code register is also cleared. When the interrupt is recognized, the current state
of the machine is pushed onto the stack and the interrupt mask bit in the condition code register
is set. This masks further interrupts until the present one is serviced. The service routine address
is specified by the contents of $FFF6 and $FFF7.
Refer to section 5.1 for detailed description of Programmable Timer.
4.2.5

M-Bus Interrupts

M-Bus interrupt is enabled when the M-Bus Interrupt Enable bit, MIEN of M-Bus Control register
is set, provided the interrupt mask bit of the condition code register is cleared. There are three
causes of M-Bus interrupt:
MOTOROLA
4-8
Address bit 7
$11 ICF
TOF is set during the counter transition of $FFFF to $0000. It is cleared by
reading the TSR (with TOF set) followed by reading the counter least significant
byte ($19).
The appropriate OCF is set when the corresponding Output Compare register
matches the Counter register. It is cleared by reading the TSR (with OCF set)
and then accessing the corresponding Output Compare register least significant
byte ($15 or $17).
ICF is set when a proper edge has been sensed by the input capture edge
detector. It is cleared by an CPU read of the TSR (with ICF set) followed by
accessing the Input Capture register least significant byte ($13).
RESETS AND INTERRUPTS
bit 6 bit 5 bit 4 bit 3
OC0F OC1F TOF TCAPS
State
bit 2 bit 1 bit 0
on reset
0 0 0 0000 u000
MC68HC05T16
TPG