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2.5.4
Pin Descriptions
Table 2-5
87C552 Pin Descriptions
Mnemonic
Pin No.
V
2
DD
STADC
3
PWM0#
4
PWM1#
5
EW#
6
P0.0-P0.7
57-50
P1.0-P1.7
16-23
16-21
22-23
16-19
20
21
22
23
P2.0-P2.7
39-46
P3.0-P3.7
24-31
24
25
26
27
28
29
30
31
Type
I
Digital Power Supply: +5V power supply pin during normal operation,
idle and power-down mode.
I
Start ADC Operation: Input starting analog to digital conversion (ADC
operation can also be started by software).
O
Pulse Width Modulation: Output 0.
O
Pulse Width Modulation: Output 1
I
Enable Watchdog Timer: Enable for T3 watchdog timer and disable
power-down mode.
I/O
Port 0: Port 0 is an 8-bit 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. Port 0 is
also used to input the code byte during programming and to output the
code byte during verification.
I/O
Port 1: 8-bit I/O port. Alternate functions include:
I/O
(P1.0-P1.5): Quasi-bidirectional port pins.
I/O
(P1.6, P1.7): Open drain port pins.
I
CT0I-CT3I (P1.0-P1.3): Capture timer input signals for timer T2.
I
T2 (P1.4): T2 event input.
I
RT2 (P1.5): T2 timer reset signal. Rising edge triggered.
I/O
SCL (P1.6): Serial port clock line I
I/O
SDA (P1.7): Serial port data line I
the lower order address byte during EPROM programming and
verification. A0 is on P1.0, etc.
I/O
Port 2: 8-bit quasi-bidirectional I/O port. Alternate function: High-order
address byte for external memory (A08-A15). Port 2 is also used to
input the upper order address during EPROM programming and
verification. A8 is on P2.0, A9 on P2.1, through A12 on P2.4.
I/O
Port 3: 8-bit quasi-bidirectional I/O port. Alternate functions include:
RxD(P3.0): Serial input port.
TxD (P3.1): Serial output port.
INT0 (P3.2): External interrupt.
INT1 (P3.3): External interrupt.
T0 (P3.4): Timer 0 external input.
T1 (P3.5): Timer 1 external input.
WR (P3.6): External data memory write strobe.
RD (P3.7): External data memory read strobe.
Name And Function
C-bus.
2
C-bus. Port 1 is also used to input
2
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