AT89S53
EA/VPP
External Access Enable. EA must be strapped to GND in
order to enable the device to fetch code from external pro-
gram 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
CC
for internal program execu-
tions. This pin also receives the 12-volt programming
Table 1.
AT89S53 SFR Map and Reset Values
0F8H
0F0H
0E8H
0E0H
0D8H
0D0H
0C8H
0C0H
0B8H
0B0H
0A8H
0A0H
98H
90H
88H
80H
IP
XX000000
P3
11111111
IE
0X000000
P2
11111111
SCON
00000000
P1
11111111
TCON
00000000
P0
11111111
TMOD
00000000
SP
00000111
TL0
00000000
DP0L
00000000
TL1
00000000
DP0H
00000000
TH0
00000000
DP1L
00000000
TH1
00000000
DP1H
00000000
SPDR
XXXXXXXX
PCON
0XXX0000
SBUF
XXXXXXXX
WCON
00000010
SPSR
00XXXXXX
PSW
00000000
T2CON
00000000
T2MOD
XXXXXX00
RCAP2L
00000000
RCAP2H
00000000
TL2
00000000
SPCR
000001XX
TH2
00000000
ACC
00000000
B
00000000
0FFH
0F7H
0EFH
0E7H
0DFH
0D7H
0CFH
0C7H
0BFH
0B7H
0AFH
0A7H
9FH
97H
8FH
87H
enable voltage (V
PP
) during Flash programming when 12-
volt programming is selected.
XTAL1
Input to the inverting oscillator amplifier and input to the
internal clock operating circuit.
XTAL2
Output from the inverting oscillator amplifier.
5
0787E–MICRO–3/06
ATMEL [ ATMEL CORPORATION ]
