A musical bell that can do everything based on the Z80 microprocessor. Scheme, description

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A musical bell that can do everything based on the Z80 microprocessor. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Microcontrollers

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The topic of electronic home calls has been repeatedly discussed on the pages of various amateur radio magazines, and, nevertheless, always arouses keen interest, because on the one hand, a call that has even the most beautiful and pleasant sound sooner or later gets bored, and on the other, You can always come up with something original, your own, like nothing else. I propose to the readers an electronic call, assembled on the basis of the popular 8-bit microprocessor Z-80, which can "play" any digitized sound into the speaker with a sampling rate of 22 kHz and a duration of more than a second.

This digitization is recorded in UV-ROM together with a small executable program in Z-80 machine codes. The use of flash ROM makes it easy to change the sound of the call without the use of a soldering iron. By the way, the choice of the Z-80 processor as the basis is dictated mainly by its low cost and general availability. And although designing a bell based on a whole microcontroller is very reminiscent of "hammering nails with a wristwatch", nevertheless, the result turned out, in my opinion, cheap and cheerful. :-)

The scheme is shown in the figure.

Rice. 1. Scheme of a musical call (click to enlarge)

The 27C512 microcircuit, which occupies the entire address space of the processor, is used as a memory, and the 1533IR23 register is used as a port. The outputs of the Q0 - Q7 register are connected to the simplest resistor digital-to-analogue converter, which generates a ready-made audio signal, which remains to be filtered from unwanted ultrasonic components by the capacitor C1, adjusted to the most suitable volume with the potentiometer R17 and amplified in power by the K174UN14 microcircuit. The power of the amplifier is enough even for hearing impaired users.

Since the processor works with only one memory chip, only in read mode and only with one port in write mode, it turned out to be possible to completely abandon the address decoder and simplify the chip selection circuit as much as possible, using only two signals MREQ and IORQ of the processor. The reset is organized on the elements R21, C7 and VD1, the master oscillator that generates a meander with a frequency of 4 MHz is made on the elements DD3.1 and DD3.2. using a quartz resonator BQ1. The call is started on the arrival of the log. "0" to the input of a hardware maskable interrupt (signal INT). Node DD3.5, DD3.6, R23, C8, VD3 serves to protect against interference that occurs on the wires leading to the bell button KH. The digital part of the call is powered by +5V voltage, stabilized by the KR142EN5A microcircuit.

A few words about the "firmware". The executable code is located at addresses 0000H - 009FH:

0000 F3 3E 80 D3 7F 3E E0 BA ED 56 30 05 FB 00 16 FF 0010 76 FB 06 FF 48 06 FF 10 FE 41 10 F8 10 FE 01 0 0020 FE 00 ED 21 0 3 7 56 06 ED 06 FF C10 43 42 26 0030 03 03E 16 D16 7F 00 06 FA 02 AF D46 42F 3 FB 80 3 EF AF BA 7 0040 10 42 C3 7 10 C41 10 26 02 F15 0050 7 16V F80 7D 77F 61E 76F 7 32D 32D 6D 7D 6D 6D 6D 6D 0060D 2D 2D 2D 2D 2D 2D 2D 2 2 2 2 2 2 2A 2 2C 0070 00C 28 63 29 20 4 75 6 79 2 20 31 39F 39 37 00 0080 00B 53 74B 6E 72 63D 68E 61 6 20D 4D 2D 20D 4D 2D 00D 0090D 2D 2D 2D 2D 2D 2D 2D 2D MONO. The only thing to do before using such a file is to delete its header in any simple editor (for example, built into Volkov Commander).

The author usually does this:

1. A .WAV file is taken that needs to be played back by a call.
2. The file is converted to the 22 kHz MONO format by any program that allows you to do this (for example, SOUNDRECORDER included in the MS WINDOWS distribution).
3. In the same SOUNDRECORDER'e the file is edited so that it takes no more than 65536 bytes.
4. The editor built into Volkov Commander checks the length of the file and, if it is no longer than 65536 bytes, the first 160 bytes of this file are removed and 160 bytes of the above code are manually typed instead.
5. Using the programmer, the PROM is "flashed".

For greater efficiency, you can abandon the LED and use a processor made using K-MOS technology, for example, KR1858VM3.

Author: K.Storchak, Kiev; Publication: cxem.net

See other articles Section Microcontrollers.

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