Is CPU08 address bus frequency 8MHz?

[admin]

Hi,

In the datasheeto of CPU08, it's said that one of the CPU08 features is 8-MHz CPU standard bus frequency. What's the meaning of this "standard bus frequency", is it the internal address bus frequency or the internal data bus frequency?

Thanks,

Simon

[bigmac]

Hello Simon,

This means that the maximum allowable internal bus frequency has been "standardised" to 8MHz over all HC908 devices.  (This limit is not applicable to the newer 9S08 devices.)

The internal bus frequency determines the CPU cycle period, that determines the execution period required for each section of code.  For devices that do not contain or use a PLL module, the frequency of the internal oscillator, external clock, or external crystal will usually be four times the internal bus frequency.

Regards,

Mac

[admin]

Hi Mac,

Thanks for your help.

Anohter question, is there any other document except "CPU08 Reference Manual" which can gives more details about the principle of the CPU08? In the "CPU08 Reference Manual" (CPU08RM.pdf), there is a section "Internal Timing" to explain the CPU08 internal timing detail, but it doesn't provide enough details such as why the CPU08 derive its timing from a 4-phase clock, where this 4-phase clock comes from?

Thanks,

Simon

[eckhard]

Hello,

there is an Application Note  AN2627 that gives more details about the internal Timing.

http://www.freescale.com/files/microcontrollers/doc/app_note/AN2627.pdf?WT_TYPE=Application%20Notes&...

Eckhard

[admin]

Hi Eckhard,

Thanks.

Regards,

Simon