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Richard Erlacher
04/01/13 14:20
Read: 952 times
Denver, Co

#189598 - I wouldn't expect too many comments
Responding to: Kalpak Dabir's previous message

I don't have this book, much less, its Indian 2nd edition. However, No one who's ever used an 805x is unaware that the I/O pins of the MCU go to the high-voltage state until programmed otherwise, either by generating an external address (due to the MOVX opcode) or by setting a low value to one or more of the port bits. Further, no one who's ever used an 805x is unaware that the I/O pins are incapable of driving a substantial load, and, hence, it is necessary to buffer them with some active device capable of sinking/sourcing sufficient current to do the job. That's probably what those transistors do. If the author has chosen a non-inverting buffer, e.g. an NPN bipolar transistor, then he clearly doesn't care that the transistor is active for a time. This indicates that he's either writing a text or that he's totally ignorant. If the transistor is a PNP bipolar or P-MOSFET, then he's wise enough to do things in a way that prevents the relay, or whatever the load is, from being energized until the port pin driving the base, and presumably the pullup resistor, the purpose of which is to ensure that its base/gate remains in its inactive state until the pin is driven otherwise.

Why not get a book written by someone who knows how to use a microcontroller? The use of one of the inverting darlington drivers, e.g. ULN200x, suggests that the author has no concern about reasonable implementation of his circuits. I haven't looked for one of these texts in many years, but I suspect that good ones are ut there. I've found, however, that, in recent years, textbooks and often manufacturers' app-notes have been wrong more often than they've been right. One has to have a command of the basics before wading into this field. In the case of the subject textbook, I suspect that correct circuit design has been left as an exercise for the student.

Since that book probably isn't widely popular outside India, I wouldn't expect much help from people who've read it.

List of 11 messages in thread
Wrong circuits in Mazidi's "8051 Microcontroller....."       Kalpak Dabir      03/31/13 10:28      
   I wouldn't expect too many comments      Richard Erlacher      04/01/13 14:20      
      my most painful "textbook experience"      Erik Malund      04/01/13 15:35      
      RE: "that book probably isn't widely popular outside India"      Andy Neil      04/01/13 16:02      
         Is it possible that one institution or teacher is the cause?      Richard Erlacher      04/01/13 19:28      
            Probably the author's own institution?      Andy Neil      04/02/13 02:41      
         The reason for my post      Kalpak Dabir      04/10/13 04:48      
            Have you fed-back to the authors?        Andy Neil      04/10/13 11:10      
   clicking relays      Erik Malund      04/01/13 15:37      
   Website - contact here?      Andy Neil      04/02/13 02:43      
   More problems with that book      Andy Neil      04/02/13 08:38      

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