Card Readers, Cmll, Cr11 - Digital Equipment pdp11 Handbook

2.5 PUNCHED CARD READER - CRll AND MARK SENSE CARD READER - CMll
Model CRll Card Reader reads EIA standard 80-column punched data cards at
300 cards per minute; model CMll reads 40-column mark-sense cards, which
can have punched holes, at 200 cards per minute.
The punched card reader uses a vacuum picker which works in conjunction with
riffle air so that card wear is insignificant, card jam virtually impossible and the
reader extremely tolerant of damaged cards. The riffling action separates the
cards in the input hopper to prevent sticking.
T~e
picker uses a strong vacuum to
grasp the bottom card and deliver it to the read station on demand. The picker
and associated throat block prevent the unit from multiple picking to the extent
that taped or stapled cards are not allowed to enter the card track. In such cases
the reader stops with pick check alarm. The operator can separate the cards and
enter them into the input hopper for normal reading. The card track is very short,
so that, only one card isin motion at a time. The combination of damaged card
tolerance, gentle card handling and short card track provide virtually jam-proof
operation.
2.5.1 Operation
Cards are read by column, beginning with Column 1. A select instruction starts
the card moving past the read station. Once a card is in motion, all 80 columns
are read. Column information is read in one of two program-selected modes: card
image or compressed code. In the card image mode 12 information bits in one
column are loaded into the data buffer and are available to the program at CRBI
address. In the compressed code mode, the card image is encoded into 8-bit bytes
and is available to the program at CRB2 address. A punched hole is interpreted as
binary 1, and the absence of a hole as binary 0
2.5.2 Programming
REGISTER.
Card Reader Status (CRS)
Card Reader Data Buffer (CRBl)
Card Reader Data Buffer (CRB2)
Card Reader Status Register (CRS)
15 14 13 12 11 10 9 8 7
ERROR---.1~
tillJU'
CARD
DONE~
CARD SUPPLY ERROR
CARO READER CHECK
TIMING ERROR
READER TO ON LINE
8USY----------~
READER READY STATUS _ _ _ _ _ _ ---J
COLUMN DONE - - - - - - - - - - - - - '
ADDRESS
777160
777162
777164
6 5 4 3 2
INTERRUPT E N A B L E - - - - - - - - - - - - - J
E J E C T - - - - - - - - - - - - - - - - - - - - - - - . J
o
R E A O - - - - - - - - - - - - - - - - - - - - - - - - - - - - J
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