Different size of data

[John99407]

one question is bothering me. assume I have a 32 bit MCU and 8 bit X device What happens if MCU send data to X device and Read data from X device. MCU size is 32 bit when It send 32 bit to X. Device X will receive 32 bit data.

Size of X device is 8 bit so it will only send 8 bit data and size of MCU 32. What happen when Device X send 8 bit to MCU? MCU will receive 8 bit data but 24 bits will be waste? Does it happen ?

 

[KlausST]

Hi,

it depends on the device and it´s interface you are using.

Klaus

 

[John99407]

Hi,

it depends on the device and it´s interface you are using.

Klaus

Let's say 32 bit MCU cortex M0 and ADC0804
ADC read 8 bit data and send it to cortex M0

 

[KlausST]

Hi,

it still does not mention the interface.

32 bit cortex M0 MCUs may have
* no dedicated parallel interface (workaround via port access, various possible commands)
* 8 bit parallel interface
* 16 bit parallel interface
* 32 bit parallel interface

In other words:
* How is it connected (hardware, schematic)
* and how do you access it (software, commands)

Klaus

 

[G4BCH]

24 bits will be waste?

If you are referring to the internal storage of the 32 bit device, then potentially yes, it depends on how you pack the data into the 32 bit word. One byte stored and the remaining 24 bits are unused, 4 bytes stored and all bits are used.