Datasheet

6
2487D–MICRO–6/08
AT89S51
EA should be strapped to V
CC
for internal program executions.
This pin also receives the 12-volt programming enable voltage (V
PP
) during Flash programming.
4.11 XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
4.12 XTAL2
Output from the inverting oscillator amplifier
5. Special Function Registers
A map of the on-chip memory area called the Special Function Register (SFR) space is shown in
Table 5-1.
Note that not all of the addresses are occupied, and unoccupied addresses may not be imple-
mented on the chip. Read accesses to these addresses will in general return random data, and
write accesses will have an indeterminate effect.