at89c51re2-slsem ATMEL Corporation, at89c51re2-slsem Datasheet - Page 6

• Manufacturer Part Number: at89c51re2-slsem
• Description: At89c51re2 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

6
V
Vss1
V
P0.0-P0.7
P1.0-P1.7
P2.0-P2.7
P3.0-P3.7
SS
CC
Mnemonic
AT89C51RE2
43-36
24-31
13-19
LCC
2-9
11,
22
44
13
14
11
2
3
4
5
6
7
8
9
Pin Number
VQFP 1.4
37-30
40-44
18-25
7-13
1-3
16
39
38
40
41
42
43
44
5,
1
2
3
5
7
8
Table 2. Pin Description
Type
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
O
I
I
I
I
I
I
I
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 V
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_0 (P3.0): Serial input port
TXD_0 (P3.1): Serial output port
INT0 (P3.2): External interrupt 0
7663B–8051–03/07
CC
or V
SS
in