TallyGenicom Matrix Printer Programmer's Manual page 161

"a"
"b"
Data which will exceed the right margin are discarded.
STOP
The vertical movement cannot be defined smaller than the current print density:
density must not be changed within Graphics Mode.
Avoid moving the print position upwards while in Graphics Mode.
This sequence is valid only in Graphics Mode ( ESC ( G, see page 67 ).
After printing raster graphics the actual print position is the most right dot + 1 dot
of the image.
Counter (a) and counter (b) can be mixed within the same sequence.
The dot count should be a multiple of 8. Otherwise the remaining data < 8 will be
discarded.
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Counter specifies the number of data bytes following:
(counter byte) + 1 = (number of data bytes to follow) or
(counter byte) = (number of data bytes to follow) – 1
128 ≤ (counter byte) ≤ 255
Counter specifies the number of times to repeat the next byte of data:
256 – (counter byte) + 1 = (number of times to repeat next byte)
(counter byte) = 257 – (number of times to repeat next byte)