6.7. Interrupt System
The T89C51RD2 has a total of 7 interrupt vectors: two external interrupts (INT0 and INT1), three timer interrupts
(timers 0, 1 and 2), the serial port interrupt and the PCA global interrupt. These interrupts are shown in Figure 16.
from high to low priority
Figure 16. Interrupt Control System
Each of the interrupt sources can be individually enabled or disabled by setting or clearing a bit in the Interrupt
Enable register (See Table 18.). This register also contains a global disable bit, which must be cleared to disable
all interrupts at once.
Each interrupt source can also be individually programmed to one out of four priority levels by setting or clearing
a bit in the Interrupt Priority register (See Table 19.) and in the Interrupt Priority High register (See Table 20.).
shows the bit values and priority levels associated with each combination.
The PCA interrupt vector is located at address 0033H. All other vectors addresses are the same as standard C52
Rev. F - 15 February, 2001