IBM 5251 Series Maintenance Information Manual page 187

Frame two (data byte and control bits)
3 4 5 6 10 11 12
13
14
o
1 2
~
l~ ~-"""'"----~
..
~-
Fill Bits
(always
000)
Parity ID
Column Address
(0- 79)
Bits 0 through 15 are used to send light pen data from
the 5251 Models 1 or 11.
Bits 7 through 14 is the data byte from the light pen
card.
The binary value of bits 8 through 14 is the column
address of the selected field. The decimal values of
these bits are:
64 32 16 8 4 2
Example:
It
o
1 1 0 1 0 1
=
a column address of 53.
The remaining frames of the 16-frame response (16
bytes of data) are not used with the Light Pen feature.
They are null and contain hex FF in the data field (bits 7
through 14).
15
lsync
Features 5251/MIM 5-7