Hi, my friends. I found the IC 74LS164 can be used for serial to parallel shift. I want to use this IC connect to PC's serial port (RS232/DB9) and control 8 LED on or off. I want to use INT 14H to send the data. Does any friend can give a example how to make this circuit work?
Hi, my friends. I found the IC 74LS164 can be used for serial to parallel shift. I want to use this IC connect to PC's serial port (RS232/DB9) and control 8 LED on or off. I want to use INT 14H to send the data. Does any friend can give a example how to make this circuit work?
It's not a good choice, a PC serial port usually sends out at least a 10 bit data word (including one start bit and one stop bit) - you could use an old UART chip to do it, or a PIC makes it even easier - one of my tutorials does exactly what you want!.
Perhaps a better choice is to use the PC's parallel port? Hm, now I'm wondering if it's possible to control one data pin. I mean, if you send data to 0x378, the controller will probably send them in parallel.
The PC's RS232 serial port follows a protocol so you must make your external device RS232 compliant.
Thank you, Nigel.
I want to know how INT 14H effect the serial bit/bits, and how to apply INT 14H for control purpose.
And also most devices connect to computer using serial single, I really want to know how a serial single (e.g. RS232) transfer and recieve.
Thank you, Nigel.
I want to know how INT 14H effect the serial bit/bits, and how to apply INT 14H for control purpose.
And also most devices connect to computer using serial single, I really want to know how a serial single (e.g. RS232) transfer and recieve.
It's been a LONGGGGGG! time since I used DOS, but I did write my own Turbo Pascal routines (as a Unit) which I used for many years for all sorts of RS232 interfacing.
As far as I can remember you basically load your data byte into the UART and call an INT routine, it's quite simple to do. The most complicated part is probably the setting up of the port in the first place.
There's nothing much to know about the external interface, the byte you load in the UART is simple sent out (high bit first), preceeded by the specified start bits, and followed by the specified stop bits.
My PIC RS232 tutorial shows you what the diagram looks like.