HP 7470A Interfacing And Programming Manual page 93

In illustrations 4 and 5, P1 is moved to the lower-right corner and P2
becomes the upper-left corner. Now (P2X—Plx) is negative. The DR command
as given is DR3,—2;the run parameter of the DR instruction is multiplied '
by -1 and the effective DR command becomes DR—3,—2placing the
directional line in the third quadrant. The negative SI height parameter
mirrors the label from top to bottom. In illustration 5, both SI parameters
are negative and the label is mirrored in both directions, making it appear
upright.
Use of DI and SR
When the DI command is used with SR, only the DI command affects
the directional baseline of labels; changes in the relative positions of P1
and P2 do not affect the baseline. Mirroring about this baseline will
occur when either a negative SR width or height parameter with a posi­
tive difference (P2x —Plx) or (P2y —Ply) or a positive SR parameter
and a negative difference are present. If respective parameters and dif­
ferences are both positive or both negative, no mirroring will occur. ­
Label direction is horizontal for all illustrations in this section. The
first three illustrations are drawn with P1 and P2 at their power-on
LABELING 5-23