Campbell Scientific CR10 CR10 Measurement and Control - Page 141

TRANSPARENT

MODE

The

SDI-12

transparent

mode is used

to

communicate directly with a SDI-12

sensor.

A

common application of the

transparent

mode

is

to

verify

proper SDI-12 sensor operation.

A computer or

terminal

is required

to

use

the

transparent

mode;

the CRlOKD

(keyboard

display)

cannot

be

used.

Transparent

mode

is

entered while the

computer

is

in

telecommunications with

the SDI-12

recorder

CR10 (at the

asterisk'*'prompt). Enter'pX'at

the

asterisk

prompt,

where'p'is

the

Control Port

number (1-8) attached to

the

SDI-12

data

line.

The CR10

responds with

a'<'prompt.

Any SDI-

12

command

preceded with

the

sensor address

and followed with

an

exclamation

point'!'

may

then be

entered.

For example,

entering'01!'at

the'<'

prompt

would

request identification from

a SDI-12

sensor

addressed at

0.

The'<'

prompt will not

appear

untilthe

recorder

CR10

finishes

executing all program tables.

While in

transparent

mode, scheduled

tables

in

the

recorder CR10

will

not execute.

Transparent

mode ends when

a

response

is

received and displayed, if no response

is

received from

the

SDI-12 sensor within

the

time-out period

following

a

valid command

(approximately

1/3

second), or

if

the

user does

not enter

a

command

before

the

mode times

out

(approximately 35 seconds). Security must

be unlocked

to

level

2

before the

Transparent

mode is used.

***

106

SDI-12

SENSOR

""

lnstruction

106 allows a CR10

to

be used as a

SDI-12

sensor.

The

CR10

can

make

measurements and

transfer data

using SDI-12

commands in

response

to another

SDI-12

recorder.

Instruction 106

is

only

in

standard

PROM OSl0-1.1.

Instruction 106 supports

the

standard SDI-12

commands as

listed

in

the

Parameter

2

description

for

Instruction

105.

The

SDI-12 data line is attached

to Control

Port

8

and

Instruction 106 must

be

the

first

instruction in Subroutine

98located

in

Table

3.

A

SDI-12 recorder addresses

the

SDI-12 sensor

CR10 by sending

a

Break and

the

sensor's

address.

The

sensor CR10 will call subroutine

98

whenever

it

detects activity on the SDI-12

SECTION

9.

INPUT/OUTPUT

INSTRUCTIONS

data

line attached

to

Port 8, but

if

the

Break and

the

specified address

are

not received by

Instruction

106,

the

remainder of

the

subroutine

is not executed.

Two

programming

techniques

exist

for

obtaining

measurement values

to

be

transferred

by

the

sensor

Instruction

106.

The'first technique

makes

the

requested

measurements

"on

demand" in

response

to

the recorders

request.

The

measurement instructions

are

located

in

Subroutine 98 and are executed only when

the

SDI-I2

recorder

requests

measurements.

This

technique

is preferred

when

measurements are

to be

made

at

the recorde/s

command.

The

second

technique transfers

measurement

values

previously obtained by instructions

in

Table

1

or Table

2.

Subroutine 98 contains only

Instructions 106

(SDl-12

sensor) and

95

(End).

When

the

recorder

requests

measurements,

values already in

the

specified input locations

are

used.

The

advantage

of

this

technique

is

that

the

sensor CR10

can be

making and

storing

measurements independent of

the

SDI-

12

recorder.

The

data

is

also

returned slightly

faster

since

the sensor

CR10

does

not make

measurements when

the recorder

requests

data,

but

rather

uses

measurements made at

the

last regular

table

execution.

These two techniques

can

be

combined allowing

the sensor

CR10 to

function

as

a

SDI-12 sensor

and

to

make

independent measurements. While

Subroutine

98

is being

executed, normalTable

1

or 2 execution

scheduling

may be altered or

missed since Subroutine

98

is not interrupted.

This

is likely to

occur

if Subroutine 98 execution

takes

longer than

the scan

interual programmed

for

Table

1

or

2.

lt

is

also possible

for

instructions

in

Table

1 or 2

to

prevent Subroutine

98

from

being

called

in

time

for

Instruction

106

to

receive the

address

information from

the

recorder. This

is likely to occur

only

if

Table

1

or

2

is

executed often and has instructions that

take

longer

than

1/3

second to

execute.

For

example,

Instruction

4

(Excite-Delay-SE) with a

1/2

second

delay could cause Subroutine

98

to

miss

the

SDI-12

address

information if

it

were

executing when

the

SDI-I2

data

line became

active.

lf this occurs the sensor CR10

will

not

respond to

the SDI-12

recorder.

Most

instructions execute fast enough that when

Instruction 106 misses

the

initial SDI-12 address,

a subsequent retry by

the

recorder will work.

9-17

Campbell Scientific CR10 CR10 Measurement and Control - Page 141

a'<'prompt.

Page 141 highlights