IBM 3277 Troubleshooting Manual page 84

generator logic card in location K2. Maintenance of the
display station is not affected by the presence of the ASCII
option; however, if logic card K2 must be changed, the
same type number card must be used.
6.4.2 ASCII Keyboards (Optional Features)
Two ASCII typewriter keyboards can be attached to the
3277 Display Station. Tt-ey are similar to EBCDIC type-
writer keyboards described in paragraph 6.3.1.1, except
unique ASC II characters are included on some key tops. PF
keys 1-12 are included in the 78-key version. ASCII
keyboards are serviced like EBCDIC keyboards, and opera-
tionally they are the same. Unique logic cards are not used,
but ASC II character generator option A or B must be
installed to enter and display the unique ASCII characters.
Option A provides the 64 ASCII character set including the
symbols I (logical or) and -, (logical not). Option B
provides the 64 ASCII character set but substitutes !
(exclamation point) for logical or and 1\ (circumflex) for
logical not.
6.5 REFERENCE DIAGRAMS
Diagrams 6· 7 through 6-14 contain reference data that can
be helpful in maintaining IBM 3277 Display Stations.
Display station data flow is shown in Diagram FO-l, a
foldout page located at the back of this manual. Diagram
6-8 lists all logic cards used in the display station and
describes the function of each card. All logic card I/O pins
used as probe points in the troubleshooting diagrams
(Section 4) are listed in Diagram 6-9. ALD references are
also listed. Logic board jumpering data for the various
keyboard feature options is included in Diagram 6-10.
Diagram 6-11 shows how characters are encoded in the
keyboard assembly. Diagrams 6-12 and 6-13 show logic
card plugging for the one-half and two-thirds boards,
respectively. Logic board pin identification data is given in
Diagram 6-14.