RCA RMB-167 - Manual (Page 32)

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P Port Data
The P command is used to read from or write to the ports. Pn displays the current value of port n.
If port n is an input port, then the value read is the current voltage levels applied to the ports. If
port n is an output port, Pn returns the current output value to port n. Pn=mmmm sets the current
value of output port n to mm.
Note that individual bits of the ports may be programmed as input or output. Thus, the word
returned by Pn gives the external voltage levels applied to the input bits and the current values of
the output bits.
W
Word Memory
This command is identical to the M command, except that the memory contents are displayed and
modified as words (2 bytes). Words start at even address.