at89s52-33sc ATMEL Corporation, at89s52-33sc Datasheet - Page 6

• Manufacturer Part Number: at89s52-33sc
• Description: At89s52 , 8-bit Microcontroller With 8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

4.9
4.10
4.11
4.12
5. Special Function Registers
6
PSEN
EA/VPP
XTAL1
XTAL2
AT89S52
Program Store Enable (PSEN) is the read strobe to external program memory.
When the AT89S52 is executing code from external program memory, PSEN is activated twice
each machine cycle, except that two PSEN activations are skipped during each access to exter-
nal data memory.
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
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
Output from the inverting oscillator amplifier.
A map of the on-chip memory area called the Special Function Register (SFR) space is shown in
Table
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
2) and T2MOD (shown in
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.
5-1.
Table
CC
for internal program executions.
10-2) for Timer 2. The register pair (RCAP2H, RCAP2L) are the
PP
) during Flash programming.
1919C–MICRO–3/05
Table 5-