參數(shù)資料
型號： ATWEBDVK-02VOIP
廠商： Atmel
文件頁數(shù)： 44/137頁
文件大?。?/td> 0K
描述： KIT DEV TCP/IP AT89C51RD2 VOIP
標準包裝： 1
系列： @Web
主要目的： *
嵌入式： *
已用 IC / 零件： AT89C51RD2
主要屬性： *
次要屬性： *
已供物品： 板，帶 VoIP 模塊和軟件
產(chǎn)品目錄頁面： 617 (CN2011-ZH PDF)
14
4235K–8051–05/08
AT89C51RD2/ED2
5.
Port Types
AT89C51RD2/ED2 I/O ports (P1, P2, P3, P4, P5) implement the quasi-bidirectional output that
is common on the 80C51 and most of its derivatives. This output type can be used as both 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 pulled low, it is driven strongly and able to sink a fairly large current. These features are
somewhat similar to an open drain output except that there are three pull-up transistors in the
quasi-bidirectional output that serve different purposes. One of these pull-ups, called the "weak"
pull-up, is turned on whenever the port latch for the pin contains a logic 1. The 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 "medium" 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-bidi-
rectional pin that is outputting a 1. If a pin that has a logic 1 on it is pulled low by an external
device, the medium pull-up turns off, and only the 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
medium pull-up and take the voltage on the port pin below its input threshold.
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 a brief time, two CPU clocks, in order to
pull the port pin high quickly. Then it turns off again.
The DPU bit (bit 7 in AUXR register) allows to disable the permanent weak pull up of all ports
when latch data is logical 0.
The quasi-bidirectional port configuration is shown in Figure 5-1.
Figure 5-1.
Quasi-Bidirectional Output
2 CPU
Input
Pin
Strong
Medium
N
Weak
P
Clock Delay
Port Latch
Data
DPU
AUXR.7
P
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
ATWEBDVK-02WC 功能描述:KIT DEV TCP/IP AT89C51RD2 WEBCAM RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估演示板和套件 系列:@Web 標準包裝:1 系列:PSoC® 主要目的:電源管理，熱管理 嵌入式:- 已用 IC / 零件:- 主要屬性:- 次要屬性:- 已供物品:板，CD，電源
ATWEBEVK-01 功能描述:KIT EVAL TCP/IP AT89C51AC2 RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估演示板和套件 系列:@Web 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標準包裝:1 系列:- 主要目的:電源管理，電池充電器 嵌入式:否 已用 IC / 零件:MAX8903A 主要屬性:1 芯鋰離子電池 次要屬性:狀態(tài) LED 已供物品:板
ATWEBEVK-02 功能描述:KIT SOFTWARE EVAL FOR T89C51CC01 制造商:microchip technology 系列:- 零件狀態(tài):停產(chǎn) 主要用途:接口，以太網(wǎng) 嵌入式:- 使用的 IC/零件:- 主要屬性:- 輔助屬性:- 所含物品:板 標準包裝:1
ATWEBEVK-05 功能描述:KIT EVAL MODULE RS232 TO TCP/IP RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估演示板和套件 系列:@Web 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標準包裝:1 系列:- 主要目的:電源管理，電池充電器 嵌入式:否 已用 IC / 零件:MAX8903A 主要屬性:1 芯鋰離子電池 次要屬性:狀態(tài) LED 已供物品:板
ATWEBEVK-06 功能描述:BOARD EVAL FOR CAN-ETHERNET MOD RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估演示板和套件 系列:@Web 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標準包裝:1 系列:- 主要目的:電源管理，電池充電器 嵌入式:否 已用 IC / 零件:MAX8903A 主要屬性:1 芯鋰離子電池 次要屬性:狀態(tài) LED 已供物品:板
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