Remote Processing RPC-330 - Manual (Page 41)

EXTERNAL INTERRUPT SECTION 12
Page 12-1 RPC-330
DESCRIPTION
Interrupts are useful, and even necessary, when
intermittent signals of short duration require the
processor s attention. Signals can be fr om door switches,
optical interrupters, missing pulse detectors, or other
electron ic devices. The O NIT R statem ent directs
progr am flow to a subrou tine when a n interr upt is
detected.
Two in terru pts, IN T 0 and IN T 1, are ava ilable. Both
interrupts are either internally or externally generated.
Internal interrupts are from the quadrature encoder/
counters. This section describes exter nal interrupts.
Both interrupts at connector P2 and P3 are low-going
edge sensitive. Levels are sampled by the CPU every
180 ns, so pu lse inputs to any interrupt m ust be at least
this long. Opto isolated input should have voltage
applied and/ or re moved for at least 10 micro -seconds to
ensure detection. Interrupts may be used to " wake-up"
the card from IDLE m ode.
INT 0 and /or IN T 1 may be used as inputs, inter rupts,
or both. Refer to SECTION 6, Using Interrupts as
Inputs for accessing using LINE function. When an
INT x line is used as an in put or exte rnal inter rupt, it
may not be used as a counter interrupt. O ne interrupt
may be u sed with a co unter and another m ay not, if
desired.
INT 0 is available from one of 3 sources. P2-ISOA and
P2-ISOB are optically isolated. P2-INT 0 is a non-
isolated, TTL input. The third source is from hardware
counter 0. U se jumper header H 2 for INT 0.
INT 1 is a non-isolated, TTL input from P3 or hardware
counter 1. U se jumper header H 3 for INT 1.
Available interrupts are shown in the table below.
H 2 a nd H 3 Description
Pins
1-2 Carry pulse from counter
3-4 Borrow pulse from counter
5-6 Exter nal interr upt
7-8 Carry or borr ow pulse from counter
9-10 Latched pulse using quadrature input
ONIN T source selection is through jumper H2 and H 3.
Pin [5-6] is jumper ed to enable external inter rupts.
When a counter is used, then its corresponding external
interrupt may not be used. C ounter 0 uses INT 0 and
counter 1 uses INT 1. See SECTI ON 14, Counter Inp uts
for more inform ation.
OPTICALLY ISOLATED
INTERRUPT/INPUT
ISOA a nd ISOB pr ovide an isolated , high voltage input.
Neither input is connecte d to groun d or + 5V and is
isolated to the card by at least 400 volts.
An exter nal voltage of a t least 3 volts, any polar ity, w ill
turn on the isolator. Higher voltages may be used
provided a ser ies resistor is in line to the supply. Use
the following formula to determine the series resistor
needed.
Rs = (Vi - 6) / .005
Where: Vi = input voltage
No series resistor is needed when Rs is negative.
INTERRUPT CHARACTERISTICS
Interrupts are negative going edge sensitive. This means
a n in te r r up t i s d e te c te d w he n IN T 0 or 1 go e s l ow . I N T
0 and 1 m ust go low for at least 180 ns for reliable
detection. A voltage must be applied to P2-ISOA and
ISOB (INT 0 only) for at least 10 micro-seconds. To
detect a subsequent interrupt, the line must go high or
voltage removed at P2-ISOA or ISOB for at least 10
micro-seco nds.
The status of the each interrupt line is read using the
following state ment:
100 A = LINE(8) : REM INT 0
110 A = LINE(9) : REM INT 1
When A = 1, the interru pt is high or no voltage is
a p pl ie d . W he n A = 0 , t he in te r r up t i s l ow . H 2 o r H 3
pins [5-6] must be jumpe red to read a status.
The ONIT R statement responds to interrupts on a
priority basis. When IN T 0 and INT 1 both go low
simultaneously, INT 1 is processed before INT 0. When
ONT ICK is activ e, O NIT R proc essing is delayed until
the ONTICK subroutine is completed. ONTICK can
i nt e rr u p t a n ON I T R pr o g ra m .