HP 4 FAMILY - Manual (Page 54)

Example: The Logical Operation default value is 252 (TSo),
corresponding to a logical function of:
(texture | source)
The result is computed below for both case 1 (source
and pattern opaque) and case 4 (source and pattern
transparent) on the previous page. Note that the ROP3
value of 252 results only with case 1, when both source and
pattern transparency modes are set to opaque.
Each column of destination, source, and texture values are
the input to the logical function. The result, 252, is the
value that would be sent to identify the logical operation
(source and pattern transparency modes are opaque). The
last row, “ROP3 + Transparencies (source & pattern are
transparent)” shows the result if source and pattern
transparency modes are transparent (the default
transparency mode).
Bits
7 6 5 4 3 2 1 0
Texture 1 1 1 1 0 0 0 0
Source 1 1 0 0 1 1 0 0
Destination 1 0 1 0 1 0 1 0
ROP3 (source & pattern are opaque) 1 1 1 1 1 1 0 0
(decimal 252)
ROP3 +Transparencies
(source & pattern are transparent) 1 1 1 0 1 0 1 0
Table 2-5. Logical Operation (ROP3)
2-18 Printer-Specific Differences