Measurement-computing Digital488/80A Manuel d'utilisateur télécharger pdf (Page 83)

Serial Poll Status Byte

SUMMARY

The Serial Poll Status byte is sent upon receiving the Serial Poll (

SPOLL) command from the IEEE

488 bus controller.

Bit Location Decimal Value Description

DIO1

1 (LSB) Service input transition.

DIO2

2 EDR (External Data Ready) input transition.

DIO3

4 IEEE 488 bus error.

DIO4

8 Not used; always logic 0.

DIO5

16 Ready for more commands.

DIO6

32 Not used; always logic 0.

DIO7

Service Request (

SRQ) bit.

DIO8

128 (MSB) Not used; always logic 0.

DESCRIPTION

The Serial Poll Status byte is sent upon receiving the Serial Poll (

SPOLL) command from the controller. Refer to the

Service Request Mask (M) command description for details on how the Serial Poll Status byte is affected. To enable

each bit to reflect the true status of the device, the appropriate M command must be executed. The significance of

each bit in the Serial Poll Status byte is shown below:

•

DIO1: When enabled by the M1 command, the DIO1 bit is set by a transition on the Service input line, its active

transition state determined by the Invert (

I) command I64. DIO1 is cleared after the controller Serial Polls the

Digital488/80A.

DIO2: When enabled by the M2 command, the DIO2 bit is set by a transition on the EDR input line, its active

transition state determined by the Invert (

I) command I32. DIO2 is cleared after the controller Serial Polls the

Digital488/80A.

DIO3: The DIO3 bit is set when an invalid command is sent to the Digital488/80A. The M4 command enables a

Service Request (

SRQ) to occur when an invalid command is received. The bit is cleared after the controller

sends the User Status (U) command U0, and reads the status string from the Digital488/80A.

DIO4: DIO4 is not used, and is always a logic 0.

DIO5: The DIO5 bit is set after an entire command string has been received and processed by the

Digital488/80A. The bit is cleared while the Digital488/80A is processing commands which have been received

from the controller. When used with the

M16 command, a Service Request (SRQ) is also generated when the

DIO5 bit is set. An Execute (X) command must be received before the DIO5 bit can be cleared.

DIO6: DIO6 is not used, and is always a logic 0.

DIO7: The DIO7 bit is set when the Digital488/80A generates a Service Request (SRQ). This is used by the

controller to determine that the Service Request was indeed generated by the Digital488/80A.

DIO8: DIO8 is not used, and is always a logic 0.

EXAMPLE

PRINT#1,"CLEAR08"

Line 1: Reset the Digital488/80A.

PRINT#1,"OUTPUT08;M4X"

Line 2: Select SRQ on IEEE 488 bus error.

PRINT#1,"OUTPUT08;F7X"

Line 3: Send an invalid bus command. The ERROR and SRQ LED

indicators should light up.

PRINT#1,"SPOLL08"

Line 4: The Serial Poll Status byte returned should be 84 (64+16+04). The

interpretation of this Serial Poll Status byte is as follows:

•

64 - The Digital488/80A was the source of the SRQ.

•

16 - The Digital488/80A is ready for more commands.

•

04 - There is an IEEE 488 bus error.

When the Digital488/80A is Serial Polled, the SRQ LED indicator turns off.

Digital488/80A User’s Manual

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Measurement-computing Digital488/80A Manuel d'utilisateur Page 83

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