HP 5501A Operating And Service Manual page 110

3.15 10746A Binary lnterface
The 10746A Binary lnterface (Figure 3-72) is the appropriate input/output (I/O) interface for
a wide variety of computers and controllers that require an 8- or 16-bit binary interface.
The binary interface transmits data to the controller in the form of two 16-bit binary words.
There are 16 lines for data output, so all 16 bits may be transmitted in parallel. Alternatively,
only 8 lines may be used and the data sent a s four 8-bit words. Data from the controller i s sent
to the interface card in the same format, using either the same lines or a separate set of tri-
state buffered lines that are turned off during data output from the card.
Instructions come into the binary I/O card in the form of eight-bit words on the same lines
a s data.
Controller
Command
Interface
-
Controller
Data
output
Intarface
[From Controller)
Bits 0-7
Controller
Data Output
Interface
(From Controller)
Bits 8-16 or
Not Uaed
Command and
1
!
control
, I C
Re& or Clear
Reset
. -
-
Flag
Command
'
Controller
Data Input Lines
or Common
,
Input/Output Lines
Error Null
2 , 3 ,
Reset Handshake lnstructlon Error System
and Sample Logic Lines Backplane Toleranoe Bits Lines Null
Backplane Data InputlOutput Decimal/
I J : : : : : : I
Figure 3-12. 70746A Binary lnterface Block Diagram
The transfer of an instruction or data word is controlled by a command line, which indicates
to the I/O card that the bit pattern on the input lines i s valid information, and a flag line,
which indicates to the controller that the data bits have been accepted. When data is trans-
ferred to the controller the flag line indicates valid information and the command line indi-
cates data accepted, a convention common to many I/O structures.
Because instructions and data share the same lines, the I/O structure has two modes of oper-
ation, called command mode and data mode. I n the command mode, information from the
controller is clocked into an instruction register and placed on the system backplane a s an
instruction to all the cards in the system, including the binary I/O card. The binary I/O card's
control logic then interprets the instruction from the backplane and performs the required
operation (if any). Once the instruction is clocked into the instruction buffer the controller is
free to set up the next instruction even though the transducer system may not have completed
execution of the preceding one. This allows operation with a fast controller in an interrupt
environment.