
12 8-bit Timer (T8F)
S1C17003 TECHNICAL MANUAL
EPSON
12-9
12.9 8-bit Timer Interrupts
The 8-bit timer outputs interrupt requests to the interrupt controller (ITC) when the counter underflows.
Underflow interrupt
This interrupt request generated by a counter underflow sets the interrupt flag T8IF (D0/T8F_INT register) to 1
within the T8F module.
T8IF: 8-bit Timer Interrupt Flag in the 8-bit Timer Chx Interrupt Control (T8F_INTx) Register (D0/0x4208/
0x4288))
To use this interrupt, set T8IE (D8/T8F_INT register) to 1. If T8IE is set to 0 (the default value), T8IF will not
be set to 1, and interrupt request for this interrupt cause will not be sent to the ITC.
T8IE: 8-bit Timer Interrupt Enable Bit in the 8-bit Timer Chx Interrupt Control (T8F_INTx) Register (D8/
0x4208/0x4288)
If T8IF is set to 1, the T8F module outputs an interrupt request to the ITC. An interrupt is generated if interrupt
conditions are satisfied for the ITC and S1C17 core.
Note: To prevent interrupt recurrences, the T8F module interrupt flag T8IF must be reset within
the interrupt processing routine following an 8-bit timer interrupt.
To prevent unwanted interrupts, reset T8IF before permitting 8-bit timer interrupts with
T8IE.
The 8-bit timer uses one interrupt signal for Ch.0 and Ch.1 interrupt requests to the ITC. The
same interrupt processing routine is performed regardless of which interrupt is generated.
When using both channel interrupts, read out the interrupt flag in the T8F module as part of
the interrupt processing routine and check which channel generates the interrupt.
Interrupt vectors
The 8-bit timer interrupt vector numbers and vector addresses are listed below.
Vector number: 12 (0x0c)
Vector address: TTBR + 0x30
Other interrupt settings
The ITC allows the priority of 8-bit timer interrupts to be set between level 0 (the default value) and level 7 for
each channel. To generate actual interrupts, the PSR (S1C17 core internal processor status register) IE (interrupt
enable) bit must be set to 1.
For more information on interrupt processing, see “6 Interrupt Controller (ITC).”
T8F