Is there isolation between:
- digital output signals, and the
- external pins?
In the (new) MC9S08QE128RM.pdf Reference Manual, page 112:
- the output signals PTxDn are represented as being DIRECTLY connected to the output pins.
In the (old) MC68HC908GP32.pdf (Data Sheet, 2008, page 119), or similar (original User Manual, for example...):
- there is a TRI-STATE DRIVER that isolates the signal data from the output pin.
And there is more: Data stored in the output registers, are read (when requested):
- NOT from the outside pin, but
- FROM the register's output (they are isolated !).
The difference is crucial.
- If there is NO buffering driver, and the output pin is read directly from the outside pin
(as in Read-Modify-Write instructions, like INC),
EXTERNAL conditions WILL affect those operations.
Could anybody state, for sure, that the NEW MC9S08QE128 has isolation
- between Output Data (output registers)
- the Output PINs,
as was the case on the OLD MC68HC908GP32?
I SUPPOUSE that, yes, THERE IS Isolation on the new devices too but, like the new documentation has dropped ALL references (pictorial and textual) to it, I must to KNOW for SURE.
Thanks a lot.
Luis G. Uribe C.