The format of the MSGDISP macro with the RESET parameter is:

>>-+-------+--MSGDISP--RESET--+-,UCB=-(reg)-+------------------->
   '-label-'                  '-,UCBL=addr--'   

>--+-------------------+--+----------------+-------------------->
   '-,MF=-+-L--------+-'  |        .-NO--. |   
          '-(E,addr)-'    '-,TEST=-+-YES-+-'   

>--+----------------+------------------------------------------><
   |        .-YES-. |   
   '-,WAIT=-+-NO--+-'   

RESET

Clears all existing data on the display. If you specify WAIT=NO and the last service requested was a demount, the display is not cleared.

After being cleared, the display shows the internal status of the device (for example, a message indicating that the device is ready).

UCB=(reg)—(2-12)

Specifies a register containing the UCB address for the device. Use the address of a UCB, not a UCB copy.

UCBL=addr—RX-type address, A-type address, (0), or (2-12)

Specifies the address of a list containing a maximum of 64 words. Each word in the list contains the address of a UCB representing a device whose display is to be reset. The end of the list is indicated by a '1' in the high-order bit of the last address in the list. If an error is encountered while processing the list, register 1 points to the associated UCB when you regain control.

You cannot specify UCBL with TEST=YES and WAIT=NO.

MF=L or (E,addr)

Specifies either the execute or the list form of MSGDISP. If you do not specify this parameter, the standard form of the macro is used.

L

Specifies the list form of MSGDISP. This generates a parameter list that can be used as input to the execute form. The execute form can modify the parameter list.

(E,addr)

Specifies that the execute form of the macro and an existing parameter list is to be used.

addr—RX-type address, (1), or (2-12)

Specifies the address of the parameter list.

TEST=NO or YES

Specifies whether the macro expansion is to include code that tests the UCB to determine whether message display is supported. If the result of the test is that the message display is not supported, an SVC is not invoked.

NO

Specifies that the macro expansion is not to include code that tests the UCB to determine whether the device supports message display. NO is the default?

YES

Specifies testing the UCB by the MSGDISP macro before attempting to invoke the message display service routine. You cannot specify TEST=YES if you also specify the UCBL parameter.

Requirement: TEST=YES requires you to include the UCB mapping macro (IEFUCBOB) in the source code. If this provision is not followed, a program check in expansion code might result. Programs running in AMODE 24 and invoking the MSGDISP macro with the TEST=YES parameter cannot pass the actual address of a UCB that resides above the 16 MB line. These programs must pass the captured UCB address or, if an actual address is passed, the UCB must reside below the 16 MB line.

WAIT=NO or YES

Specifies when control is to be returned to you.

NO

Specifies that the MSGDISP function is not to wait for completion of I/O initiated on the caller's behalf. When MSGDISP returns, the I/O request might still be running. I/O return codes are not returned, and I/O errors are recorded in the same manner as any permanent error by the error recovery procedure.

You cannot specify WAIT=NO if you also specify the UCBL parameter.

YES

Specifies that control is to be returned after I/O is complete.

Demount messages can be reset only if WAIT=YES is specified.