TM 5-6675-318-14
(1) data bus - 8 s i g n a l l i n e s - DIO1 through DI08,
(2) data transfer control - 3 signal lines - (Handshake),
(3) interface management - 5 signal lines.
d. The data bus transfers 8-bit data or control words between the controller and
t h e p l o t t e r . The words are in bit-parallel byte-serial form. The words are trans-
f e r r e d b i d i r e c t i o n a l l y . The three data transfer control lines, or handshake lines,
are used to control the transfer of information on the data bus. These lines are
identified as follows:
(1) Data valid (DAV) - used to indicate that valid information is
available
on the data lines.
(2) Not ready for data (NRFD) - used to indicate the readiness o f t h e p l o t t e r
to
accept information.
( 3 ) Not data accepted (NDAC) - u s e d to indicate the acceptance o f i n f o r m a t i o n
by the plotter.
e. The five interface management lines are used to provide an orderly flow of
information across the interface bus.
In the operation of the 9872C plotter on the
T h e fi v e i n t e r f a c e m a n a g e m e n t
interface bus, the remote enable (REN) is not used.
lines are identified as follows:
(1) Attention (ATN) - used by the controller to specify how data on the DIO
signal lines are to be interpreted (command, data, or parallel poll response), and
which devices on the bus must respond to the data.
( 2 ) Service request (SRQ) - u s e d t o i n d i c a t e t h a t t h e p l o t t e r n e e d s a t t e n t i o n
and to request an interruption of the current sequence of events.
(3)
Interface
clear
(IFC)
- used by the controller to place the bus in a
known quiescent condition.
(4) End or identify (EOI) - used by a talker to indicate the end of a multi-
ple-byte transfer sequence or, in conjunction with ATN, to execute a polling
sequence.
(5) Remote enable (REN) - not used.
f . Positive true logic is used within the plotter circuitry. A capital letter N
before a mnemonic, such as NRFD, shows an inversion for that line.
Power Up. W h e n D o w e r i s a p p l i e d t o t h e p l o t t e r , a r e s e t s i q n a l i s g e n e r a t e d
g.
This reset pulse is used to clear flip-flops-thus setting the
i n t h e p o w e r supply.
p l o t t e r t o a k n o w n c o n d i t i o n . T h e NDAC and NRFD lines to the controller are set
p a s s i v e t r u e i n d i c a t i n g t h i s i d l e c o n d i t i o n . T h e reset pulse can also be generated
b y pressing the RESET switch S5 on the main PCA A2. -
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