了解直流电气特性的微控制器-Understanding DC

文章摘要：This is an important parameter to understand about Port 0 on the DS80C320. Port 0 on 8051-type microcontrollers are open-drain. All other ports have internal pullup resistors. To use Port 0 as a general-purpose I/O would require some form of pullup resistance. If external pullup resistors are used o

了解直流电气特性的微控制器-Understanding DC,标签：计算机控制技术,工厂电气控制技术,http://www.88dzw.com


This is an important parameter to understand about Port 0 on the DS80C320. Port 0 on 8051-type microcontrollers are open-drain. All other ports have internal pullup resistors. To use Port 0 as a general-purpose I/O would require some form of pullup resistance. If external pullup resistors are used on Port 0, the maximum voltage on Port 0 pins do not exceed the maximum voltage value as long as the sink current does not exceed IOL. The DS80C320 is different in one respect. It has no latch on Port 0 because there is no internal program memory. Therefore, Port 0 cannot be used as a general-purpose I/O port. When addressing external-memory devices, Port 0, 2, ALE, and active-low PSEN pins do not exceed 0.45V when sinking 3.2mA.

PARAMETER	SYMBOL	MIN	TYP	MAX	UNITS	NOTES
Output High Voltage Ports 1, 3, ALE, active-low PSEN at IOH = -50µA	VOH1	2.4			V	1, 6

When the DS80C320 outputs a logic high level, the load connected to the port pin or ALE or active-low PSEN pins cause a current flow from the microcontroller to the load. The negative number for IOH indicates the current is sourced from the microcontroller. If the external load does not sink more than 50µA, the minimum output voltage measured at the pins are equal to or greater than 2.4V. The test condition used for this parameter assumes RST and VCC are at the same potential. This condition mimics operation of the pins in I/O mode.

PARAMETER	SYMBOL	MIN	TYP	MAX	UNITS	NOTES
Output High Voltage Ports 1, 3, at IOH = -1.5mA	VOH2	2.4			V	1, 7

This condition reflects the port in transition mode, i.e., changing from a 0 to 1 state. When the port pins are changed from 0 to 1, a one-shot circuit drives the port pins hard for two clock cycles to assist in a strong pullup. At the end of the two-cycle transition, a weak pullup replaces the strong pullup to hold the port in a logic 1 state. This weak pullup remains until the next 1-to-0 transition. During the 0-to-1 transition, the voltage at these pins is not less than 2.4V, provided the load does not draw more than 1.5mA from the microcontroller.

PARAMETER	SYMBOL	MIN	TYP	MAX	UNITS	NOTES
Output High Voltage Ports 0, 2, ALE, active-low PSEN at IOH = -8mA	VOH3	2.4			V	1, 5

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