6
TS8xCx2X2
4184I–8051–02/08
Mnemonic Pin Number Type Name and Function
DIL LCC
VQFP
1.4
V
SS
20 22 16 I Ground: 0V reference
Vss1 1 39 I
Optional Ground: Contact the Sales Office for ground
connection.
V
CC
40 44 38 I
Power Supply: This is the power supply voltage for normal,
idle and power-down operation
P0.0-P0.7
39-
32
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 pins must be polarized to Vcc
or Vss in order to prevent any parasitic current consumption.
Port 0 is also the multiplexed low-order address and data bus
during access to external program and data memory. In this
application, it uses strong internal pull-up when emitting 1s.
Port 0 also inputs the code bytes during EPROM
programming. External pull-ups are required during program
verification during which P0 outputs the code bytes.
P1.0-P1.7 1-8 2-9 40-44
1-3
I/O Port 1: Port 1 is an 8-bit bidirectional I/O port with internal
pull-ups. 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. Port 1 also receives
the low-order address byte during memory programming and
verification.
Alternate functions for Port 1 include:
1 2 40 I/O T2 (P1.0): Timer/Counter 2 external count input/Clockout
2 3 41 I
T2EX (P1.1): Timer/Counter 2 Reload/Capture/Direction
Control
P2.0-P2.7
21-
28
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 pulled low will source
current because of the internal pull-ups. 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 atDPTR).In this application, it
uses strong internal pull-ups emitting 1s. During accesses to
external data memory that use 8-bit addresses (MOVX atRi),
port 2 emits the contents of the P2 SFR. Some Port 2 pins
receive the high order address bits during EPROM
programming and verification: P2.0 to P2.4
P3.0-P3.7
10-
17
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 pulled low will source
current because of the internal pull-ups. Port 3 also serves
the special features of the 80C51 family, as listed below.
10 11 5 I RXD (P3.0): Serial input port
11 13 7 O TXD (P3.1): Serial output port
12 14 8 I INT0 (P3.2): External interrupt 0
