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Can I read time data from an RTC (Real-Time Clock) chip without a MCU?

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Jurek_p:
I have an HD146818 (Motorola MC146818) integrated circuit, which is a real-time clock. I would like to build a simple clock on it, which will control an 8-segment display. I read the datasheet for this chip and it is not clear to me whether the chip can operate independently without a microprocessor. My assumption is that time information such as hours, minutes, and seconds, etc. are stored in the HD146818, and access to them, i.e. reading, is done through the address pins A0-A7 (pin 15 "high"), taking into account the appropriate configuration of other pins for data reading. I assume that I can decode the A0-A7 pins (from binary to BCD) and read the time. Is this possible?

How can "I start it up"? Please advice me.

https://datasheetspdf.com/pdf-file/555707/HitachiSemiconductor/HD146818/1

Thanks Jurek

ataradov:
You read the data by writing the address of the register and then reading the value. It would be incredibly complicated circuit, essentially replicating an MCU.

This is something $1 MCU can do for you, and it would even include an RTC, so you don't need this ancient chip.

Jurek_p:
Thanks Alex,

I do not write a code (just yet:)) so I wondering if I could use an Analog Discovery 2 to use it as a write / read device? AD2 has 16 I/Os so I could write a pattern to startup the chip.
Is it sounds possible? I just want to play with this ancient chip and get to know how it works.

J

ataradov:
Yes, AD2 would work for this.  Look at the figure 10, you need to connect the signals from the Bus Interface. AD2 can only do 3.3 V levels, so this RTC should be powered from 3.3 V as well.  Setup AD2 to follow the timing diagrams.

Jurek_p:

--- Quote from: ataradov on July 21, 2023, 08:17:57 pm ---you need to connect the signals from the Bus Interface.
--- End quote ---

So I need to create a BUS with my AD2 and use appropriate channels to send and receive the informations to/from RTC, right? So all of the channels like OSC1, OSC2, CE, DS, R/W, AS and A0-A7 must be connected to with AD2?


--- Quote from: ataradov on July 21, 2023, 08:17:57 pm ---Setup AD2 to follow the timing diagrams.
--- End quote ---

So I need to set a timing digram from Figure 1,2,3?

Thanks J

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