TM 5-6675-323-14
(a) The operation of the HP-IB Interface ROM circuitry is dependent on
the requirements of the computer or plotter as indicated by the status of signals on
t h e s i g n a l l i n e s . Direction of signal flow depends on which system (computer, HP-IB
Interface, or plotter) is the active controller and, during an interchange, which
device is talking (the active controller or the HP-IB Interface) and which is
listening.
Table 3-1.
SIGNAL LINES BETWEEN COMPUTER AND INTERFACE
Signal
Direction
(CMPTR
INTFC)
Function
Line*
Description
DATA LINES
Carries all data.
Input/Output Data
IOD7
IOD
Identifies peripheral
Peripheral
Address
PA thru PA3
device to be addressed.
I/0 LINES
Register Code
L a t c h e s inputs and out-
I C 1 thru IC2
puts into register.
Determines
transfer
Direction of Transfer
DOUT
(1 = Out)
direction.
Initiates transfer.
1 / 0 Strobe
10SB
Indicates HP-IB Inter-
Interface Flag
FLG
f a c e readiness to com-
(1 = Ready)
puter.
Indicates HP-IB Inter-
Interface Status
STS
face presence to computer.
( 1 = Present)
Resets
HP-IB
Interface.
Calculator
Initialize
INIT
Low
priority
request.
I n t e r r u p t Request Low
IRL
(-7)
High priority request.
I n t e r r u p t Request High
IRH
(8-15)
D e m a n d s response to poll.
Interrupt Poll
INT
* Bar over line designation stands for negative-true logic.
3-8
