6

2601B–MICRO–03/05

AT89LS52

4.10

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the device to fetch

code from external program memory locations starting at 0000H up to FFFFH. Note, however,

that if lock bit 1 is programmed, EA will be internally latched on reset.

EA should be strapped to V

This pin also receives the 12-volt programming enable voltage (V

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.

User software should not write 1s to these unlisted locations, since they may be used in future

products to invoke new features. In that case, the reset or inactive values of the new bits will

always be 0.

Timer 2 Registers: Control and status bits are contained in registers T2CON (shown in Table 5-

2) and T2MOD (shown in Table 10-2) for Timer 2. The register pair (RCAP2H, RCAP2L) are the

Capture/Reload registers for Timer 2 in 16-bit capture mode or 16-bit auto-reload mode.

Interrupt Registers: The individual interrupt enable bits are in the IE register. Two priorities can

be set for each of the six interrupt sources in the IP register.