Port0 - 16 bit data bus

[skale9]

Posted on July 17, 2003 at 10:07

Port0 - 16 bit data bus

[skale9]

Posted on July 17, 2003 at 08:58

Hi,

Since I seem to get answers quicker on this forum, I wish ask one more question about Port0.

Port0 acts as 16-bit data bus in demultiplexed bus mode. But it can only work as 2 8-bit ports when used as ports. This seems to be tricky nomencleture because it got me confused to assume Port0 as a complete 16-bit port. If it cannot be used as one port why call it as port0 in the first place!!!!!!!!!

And if it cant be used as a 16-bit port, how does it work as a 16-bit data bus?

PLease help.

Regards

Sonali

[charles239955_st]

Posted on July 17, 2003 at 10:07

Hello,

In fact we call it ''Port0'' because of bus usage but it is made of two 8 bit physical ports named P0H and P0L for Port 0 High / Low part.

If the external bus interface is enabled (BUSCON0 to 4) and a 16 bit demultiplexed mode is selected, then the ST10 automatically ''concatenate'' this 2 ports and read/write data on 16 bits.

From user side it is transparent when P0H and P0L are used as bus because only read/write operations are performed.

On the other hand, when used as general purpose IO, the 2 parts are independant and have their own register to configure the direction and the pad latch.