AT89LP216-20PU Atmel, AT89LP216-20PU Datasheet - Page 23

• Manufacturer Part Number: AT89LP216-20PU
• Description: MCU 8051 2K FLASH 20MHZ 16-PDIP
• Manufacturer: Atmel
• Series: 89LPr

Specifications of AT89LP216-20PU

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 14
• Program Memory Size: 2KB (2K x 8)
• Program Memory Type: FLASH
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 2.4 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 16-DIP (0.300", 7.62mm)
• Processor Series: AT89x
• Core: 8051
• Data Bus Width: 8 bit
• Data Ram Size: 128 B
• Interface Type: UART, SPI
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 14
• Number Of Timers: 2
• Operating Supply Voltage: 2.4 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• 3rd Party Development Tools: PK51, CA51, A51, ULINK2
• Development Tools By Supplier: AT89ISP
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Data Converters: -
• Lead Free Status / Rohs Status: Details

13.1.1
3621E–MICRO–11/10
Quasi-bidirectional Output
Table 13-2.
Port pins in quasi-bidirectional output mode function similar to standard 8051 port pins. A Quasi-
bidirectional port can be used both as an input and output without the need to reconfigure the
port. This is possible because when the port outputs a logic high, it is weakly driven, allowing an
external device to pull the pin low. When the pin is driven low, it is driven strongly and able to
sink a large current. There are three pull-up transistors in the quasi-bidirectional output that
serve different purposes. One of these pull-ups, called the “very weak” pull-up, is turned on
whenever the port latch for the pin contains a logic “1”. This very weak pull-up sources a very
small current that will pull the pin high if it is left floating.
A second pull-up, called the “weak” pull-up, is turned on when the port latch for the pin contains
a logic “1” and the pin itself is also at a logic “1” level. This pull-up provides the primary source
current for a quasi-bidirectional pin that is outputting a “1”. If this pin is pulled low by an external
device, this weak pull-up turns off, and only the very weak pull-up remains on. In order to pull the
pin low under these conditions, the external device has to sink enough current to overpower the
weak pull-up and pull the port pin below its input threshold voltage.
The third pull-up is referred to as the “strong” pull-up. This pull-up is used to speed up low-to-
high transitions on a quasi-bidirectional port pin when the port latch changes from a logic “0” to a
logic “1”. When this occurs, the strong pull-up turns on for two CPU clocks quickly pulling the
port pin high. The quasi-bidirectional port configuration is shown in
cuitry of P1.3, P3.2 and P3.3 is not disabled during Power-down (see
Figure 13-1. Quasi-bidirectional Output
PxM0.y
From Port
Register
0
0
1
1
Configuration Modes for Port x, Bit y
PxM1.y
0
1
0
1
1 Clock Delay
(D Flip-Flop)
Port Mode
Quasi-bidirectional
Push-pull Output
Input Only (High Impedance)
Open-drain Output
Input
Data
PWD
V
Strong
CC
V
Weak
Very
CC
Figure
Figure
AT89LP216
13-1. The input cir-
13-3).
V
Weak
CC
Port
Pin
23