Interrupt System
C513AO
User’s Manual
7-3
05.99
7.1
Interrupt Structure
A common mechanism is used to generate the various interrupts, each source having its own
request flag(s) located in a Special Function Register (SFR). Examples include TCON, T2CON and,
SCON. When the peripheral or external source meets the condition for an interrupt, the dedicated
request flag is set, whether an interrupt is enabled or not. For example, each Timer 0 overflow sets
the corresponding request flag TF0. If it is already set, it retains a “1”. But the interrupt is not
necessarily serviced.
Each interrupt requested by the corresponding flag can be enabled or disabled individually by the
enable bits in the SFR IE. This determines whether the requested interrupt will be performed. In
addition, there is a global enable bit for all interrupts which, when cleared, disables all interrupts
regardless of their individual enable bits.
Table 7-1
Interrupt Sources and Vector
Interrupt Source
Vector Address
Request Flags
External interrupt 0
Timer 0 interrupt
External interrupt 1
Timer 1 interrupt
USART serial port interrupt
Timer 2 interrupt
Synchronous Serial Channel interrupt (SSC)
Wake-up from power-down mode
0003H
000BH
0013H
001BH
0023H
002BH
0043H
007BH
IE0
TF0
IE1
TF1
RI + TI
TF2 + EXF2
WCOL + TC
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