Blackrock Microsystems Pro60, Programming Manual, Page: 11 / 26

TIFF combines the features of unencoded and run length
encoding. The graphic information is preceded by a control
byte. The control byte indicates (sign bit) if the following byte
is a graphic byte that is repeated (up to 127 times) or if a
number of bytes follow (up to 127) that are to be printed as a
bit map. A positive control byte expects bit map information, a
negative control byte represents repeat byte.
MODE 3: Delta row
Delta row will pick out the bytes from a line that differ from
the previous line, and transfer only these differences. If only
one bit were to differ, just the respective byte would need to be
transferred. The delta data consists of the command and 1 to 8
replacement bytes. The command byte contains two pieces of
information, the number of replacement bytes (bits 7, 6, 5) and
the relative left offset of the last byte that was cahnged (bit 4, 3,
2, 1 and 0). Value 31 as offset expects a following additional
offset byte. The offset values are summed. In text mode, from
left to right, the dot on the very right is the LS bit.
A 1 in the respective bit position of a replacement byte
represents a black dot in the line. After completing the line, the
printer will automatically return to character mode. Mixing of
text and graphics is not possible with delta row.
6.3.4 Form Control
The printer allows two types of form length control.
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Control by paper length
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Control by marker
6.3.4.1 Control by paper length
The length of the printout is set via the command <ESC> “l” xh xl. The paper length fed through
the printer mechanism is measured and considered the end of form. Strictly speaking this is not a
proper form control mechanism, it only defines a physical length of paper, starting from the current
position to be a 'form'. A start position can be set at an arbitrary point on the paper. A FF command
will cause the printer to advance to the length given by the xl,xh parameters regardless of its current
printing position.
6.3.4.2 Control by Markers
Markers on the paper are recognised by a sensor. This method of form control can be performed
with preprinted light absorbing marks on the front face of the printed paper.