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21X0A-004

Option -004

IEEE-488 Interface

604-1. INTRODUCTION

604-2. Option 21X0A-004 IEEE-488 Interface provides

the 2180A and 2190A digital thermometers with a direct

output only connection to the IEEE-488 bus.

604-3. Option 21X0A-004 may be ordered with the 2180A

and 2190A thermometers for factory installation, or is

available by itself for service center installation. Option

21XO A-004 cannot be used in a 2300A Scanner system. For

more compatibility information, refer to “Compatibility

With 2300A and Previously Produced Thermometers”.

604-4. The IEEE-488 standard connector is accessible

from the rear panel of the thermometer. The format of the

output data includes the channel number, the current read

ing, and any out-of-range or open thermocouple informa

tion. (Refer to Table 604-3.)

604-5. SPECIFICATIONS

604-6. Specifications for Option 21 XO A-004 are shown in

Table 604-1.

NOTE

The L4 listener function indicates that the

thermometer IEEE-488 bus interface has the

same 5-digit talk and listen addresses, and that

the receipt of a listen address disables the talk

address.

604-7. IEEE-488 BUS ADDRESS CODE

SELECTION

604-8. A six-position dip switch (SW3), located on

Option 21X0A-004 pea (printed circuit assembly), sets the

IEEE-488 bus address codes for the option. To gain access

to SW3, lift off the case top of the thermometer by remov

ing the six screws from the base. Referring to Table 604-2,

set positions 1 through 5 of SW3 to assign the desired

address.

604-9. OPERATION

604-10. Once Option 21X0A-004 is installed and SW3 is

properly set, make sure that the IEEE-488 cable is correctly

connected to the option to ensure that all functions are

properly monitored by the controller.

604-11. Program Considerations

604-12. Position 6 on SW3 controls the SRQ signal (Ser

vice Request) to the IEEE-488 bus. Upon receiving an

SRQ, the controller serially polls each device on the bus for

SRQ status. SRQ status of the Option 21X0A-004 is indi

cated by bit DB6 (position 64 decimal, 40 hexadecimal) in

the serial poll register (U12). With SW3 position 6 in the

ON position, SRQ is generated when a LF (line feed) is

received in the 32-byte buffer of Option 21X0A-004. The

LF character is used by the thermometer to indicate the end

of a data transfer to the Option 21 XO A-004. (Refer to Table

604-3.) Option 21X0A-004 sets DBl (2 decimal), which

causes a serial poll to return a total value of decimal 66 or 42

hexadecimal.

604-13. When the SRQ mode is enabled, the SRQ is set

when the thermometer makes a reading available to the

Option 21X0A-004. The reading is held indefinitely until

the SRQ is serviced. All new readings from the thermom

eter are discarded. When SRQ is disabled, the output

buffer is continuously updated with the most recent reading

from the thermometer. However, there may be a 0.33

second delay encountered in the returned reading. This

delay occurs when one reading is sent across the IEEE bus

and the Option 21X0A-004 waits for the thermometer to

send the next reading. An IEEE bus timeout error may

occur unless the timeout is set longer than this delay.

604-1

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