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C-17
REGISTERS
EP_REG
EP_REG
Address:
Reset State:
1FE5H
X0H
Each bit of the extended port data output (EP_REG) register contains data to be driven out by the
corresponding pin. When a pin is configured as standard I/O (EP_MODE.
x
= 0), the result of a CPU
write to EP_REG is immediately visible on the pin.
During nonextended data accesses, EP_REG contains the value of the memory page that is to be
accessed. For compatibility with software tools, clear the EP_REG bit for any EPORT pin that is
configured as an extended-address signal (EP_MODE.
x
set).
80C196NU Only: For nonextended data accesses, the 80C196NU forces the page address to 00H.
You cannot change pages by modifying EP_REG.
7 0
— — — — PIN3 PIN2 PIN1 PIN0
Bit
Number
Bit
Mnemonic
Function
7:4 — Reserved; always write as zeros.
3:0 PIN3:0 Extended Address Port Pin
x
Output
If EPORT.
x
is to be used as an output, write the data that it is to drive
out.
If EPORT.
x
is to be used as an input, set this bit.
For the 8XC196NP, if EPORT.
x
is to be used as an address line, write
the correct value for the memory page to be accessed by nonextended
instructions.
The 80C196NU forces the page address to 00H. You cannot change
pages by modifying EP_REG