T89C51RD2-SMSCM View Datasheet(PDF) - Atmel Corporation
Part Name
Description
Manufacturer
T89C51RD2-SMSCM Datasheet PDF : 104 Pages
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Table 2. Pin Description
Mnemonic
VSS
Vss1
Pin Number
DIL LCC VQFP 1.4
20
22
16
1
39
VCC
P0.0-P0.7
40
44
39-32 43-36
38
37-30
P1.0-P1.7
1-8
2-9
40-44
1-3
P2.0-P2.7
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
21-28 24-31
40
41
42
43
44
1
2
3
18-25
P3.0-P3.7
10-17 11,
13-19
5,
7-13
10
11
5
11
13
7
Type
I
I
I
I/O
I/O
I/O
I
I
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I
O
Name and Function
Ground: 0V reference
Optional Ground: Contact the Sales Office for ground connection.
Power Supply: This is the power supply voltage for normal, idle and power-down
operation
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 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.
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 TSC8x54/58 Port 1 include:
T2 (P1.0): Timer/Counter 2 external count input/Clockout
T2EX (P1.1): Timer/Counter 2 Reload/Capture/Direction Control
ECI (P1.2): External Clock for 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
CEX3 (P1.6): Capture/Compare External I/O for PCA module 3
CEX4 (P1.7): Capture/Compare External I/O for PCA module 4
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 @DPTR).In this application, it uses strong internal pull-ups
emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX
@Ri), 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 P2.5 for RB devices
P2.0 to P2.6 for RC devices
P2.0 to P2.7 for RD devices.
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.
RXD (P3.0): Serial input port
TXD (P3.1): Serial output port
6 T89C51RD2
4243G–8051–05/03
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