Xtal freq for Z8671 2K ROM BASIC, member of old Z8 family

[eblc1388]

Hi,

Can anyone remember what Xtal frequency is specified for this MCU in order to produce the correct serial baudrate? The chip Z0867108PEC has suffix "08" so the crystal frequency will certainly be less than 8MHz.

Z8671 is a 2K masked ROM BASIC Z8 variant from the '80. It has internal UART. The baudrate divisor is hard coded into the ROM and requires a particular crystal frequency to produce the correct baudrate.

Thanks

 

[eng1]

I haven't worked with that microcontroller. I've just searched the web to answer your question. Does this link help?

 

[Papabravo]

The number 7.372800 MHz. comes to mind. It is 768 * 9600baud

For the numerologists 768 = 256 * 3 = (2^8 ) * 3

 

[eblc1388]

@eng1: In fact I raised my question after reading that exact webpage in the link, which indicated twice in its content that the Xtal frequency is 7.8MHz.

After studying the ASM listing included on that page, I worked out the correct XTAL frequency should in fact be 7.3728MHz.

@Papabrave: Its exactly as what you've suggested.