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Philips Semiconductors
Preliminary data
P89C668
80C51 8-bit Flash microcontroller family
64KB ISP Flash with 8KB RAM
2001 Jul 27
5
PIN DESCRIPTIONS
MNEMONIC
PIN NUMBER
NAME AND FUNCTION
PLCC
LQFP
V
SS
V
CC
P0.0–0.7
22
16
I
Ground:
0 V reference.
44
38
I
Power Supply:
This is the power supply voltage for normal, idle, and power-down operation.
43–36
37–30
I/O
Port 0:
Port 0 is an open-drain, bidirectional I/O port. Port 0 pins that have 1s written to them float
and can be used as high-impedance inputs. Port 0 is also the multiplexed low-order address and
data bus during accesses to external program and data memory. In this application, it uses strong
internal pull-ups when emitting 1s.
P1.0–P1.7
2–9
40–44,
1–3
I/O
Port 1:
Port 1 is an 8-bit bidirectional I/O port with internal pull-ups on all pins except P1.6 and
P1.7 which are open drain. Port 1 pins that have 1s written to them are pulled high by the internal
pull-ups and can be used as inputs. As inputs, port 1 pins that are externally pulled low will source
current because of the internal pull-ups. (See DC Electrical Characteristics: I
IL
).
Alternate functions for P89C668 Port 1 include:
T2 (P1.0):
Timer/Counter 2 external count input/Clockout (see Programmable Clock-Out)
T2EX (P1.1):
Timer/Counter 2 Reload/Capture/Direction Control
ECI (P1.2):
External Clock Input to the PCA
CEX0 (P1.3):
Capture/Compare External I/O for PCA module 0
CEX1 (P1.4):
Capture/Compare External I/O for PCA module 1
CEX2 (P1.5):
Capture/Compare External I/O for PCA module 2
SCL (P1.6):
I
2
C bus clock line (open drain)
SDA (P1.7):
I
2
C bus data line (open drain)
2
3
4
5
6
7
8
9
40
41
42
43
44
1
2
3
I/O
I
I
I/O
I/O
I/O
I/O
I/O
P2.0–P2.7
24–31
18–25
I/O
Port 2:
Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. Port 2 pins that have 1s
written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, port 2
pins that are externally being pulled low will source current because of the internal pull-ups. (See
DC Electrical Characteristics: I
IL
). Port 2 emits the high-order address byte during fetches from
external program memory and during accesses to external data memory that use 16-bit addresses
(MOVX @DPTR). In this application, it uses strong internal pull-ups when emitting 1s. During
accesses to external data memory that use 8-bit addresses (MOV @Ri), port 2 emits the contents
of the P2 special function register.
P3.0–P3.7
11,
13–19
5, 7–13
I/O
Port 3:
Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that have 1s written
to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, port 3 pins that
are externally being pulled low will source current because of the pull-ups. (See DC Electrical
Characteristics: I
IL
). Port 3 also serves the special features of the P89C668, as listed below:
RxD (P3.0):
Serial input port
TxD (P3.1):
Serial output port
INT0 (P3.2):
External interrupt
INT1 (P3.3):
External interrupt
CEX3/T0 (P3.4):
Timer 0 external input; Capture/Compare External I/O for PCA module 3
CEX4/T1 (P3.5):
Timer 1 external input; Capture/Compare External I/O for PCA module 4
WR (P3.6):
External data memory write strobe
RD (P3.7):
External data memory read strobe
11
13
14
15
16
17
18
19
5
7
8
9
10
11
12
13
I
O
I
I
I
I
O
O
RST
10
4
I
Reset:
A high on this pin for two machine cycles while the oscillator is running, resets the device. An
internal diffused resistor to V
SS
permits a power-on reset using only an external capacitor to V
CC
.
Address Latch Enable:
Output pulse for latching the low byte of the address during an access to
external memory. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator
frequency, and can be used for external timing or clocking. Note that one ALE pulse is skipped
during each access to external data memory. ALE can be disabled by setting SFR auxiliary.0.
With this bit set, ALE will be active only during a MOVX instruction.
ALE
33
27
O
PSEN
32
26
O
Program Store Enable:
The read strobe to external program memory. When executing code from
the external program memory, PSEN is activated twice each machine cycle, except that two PSEN
activations are skipped during each access to external data memory. PSEN is not activated during
fetches from internal program memory.