Why is the Addr0 pin missing on Blackfin Processor EBIU?
Blackfin does not directly support 8bit addressing. If there is a need to connect to an 8bit device, it is also treated as in 16bit addressing. So in order to avoid access to ‘odd’ address locations, the A0 pin has not been provided out of the processor. Hence address lines are always from A1 to A19.
Anand, this question is asked often and you have given very good information. We can also say that some 16 bit memory systems allow the Blackfin processor to do 8bit reads and writes. The byte is selected through the ABE0# and ABE1# signals. This is commonly done with SDRAMs by using the DQML and DQMH signals.
Is ABE0# pin equivalent to A0# address line?
So, if I need to WRITE to an a 8-bit Peripheral I can Access odd or even locations of each Async bank (depending on ABE0# level), while I must READ only 16-bit odd (ABE0# = 0, always -> A0 = 1) addresses: is this correct?
Thanks a lot
ABE0# is not equivalent to A0 or A0#.
You should use 16 bit access or even address only byte access instructions to 8 bit peripherals. Normal byte addressing will put (or receive) the odd byte data on data pins D8 to D15. Byte addressing puts even byte data on data pins D0 to D7. The byte enable signals allow byte access of 16 bit memory and peripherals. This is critical during byte write operations where you only wish to change one of the 2 bytes. ABE0# can not be used as A0 to the peripheral. You would loose the data for every other byte because only 8 data pins can be connected to an 8 bit peripheral.
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