[Info-vax] disabling a CTRL/Y ast

[Tom Adams]

On Wednesday, January 6, 2016 at 10:47:51 AM UTC-5, Bob Gezelter wrote:
> On Wednesday, January 6, 2016 at 10:15:11 AM UTC-5, Tom Adams wrote:
> > Section 5.4.3.2 here:
> > 
> > http://www2.hmc.edu/www_common/OVMS072-OLD/72final/6136/6136pro_019.html
> > 
> > explains how to enable a ctrl/y ast using IO$M_CTRLYAST. It also says:
> > 
> > "This function code is also used to disable the AST."
> > 
> > but I cannot figure out the arguments of the QIOW call that would disable the AST.
> > 
> > How does one disable the AST?
> 
> Tom,
> 
> From the referenced page:
> 
> "5.4.3.2 Enable Ctrl/C AST and Enable Ctrl/Y AST Function Modifiers
> 
> Both set mode functions can take the enable Ctrl/C AST and enable Ctrl/Y AST function modifiers. These function modifiers request the terminal driver to queue an AST for the requesting process when you press Ctrl/C or Ctrl/Y. The following combinations of function code and modifier are provided:
> 
>     IO$_SETMODE!IO$M_CTRLCAST---Enable Ctrl/C AST
>     IO$_SETMODE!IO$M_CTRLYAST---Enable Ctrl/Y AST 
> 
> These function code modifier pairs take the following device- or function-dependent arguments:
> 
>     P1---Address of the AST service or 0 if the corresponding AST is disabled
>     P2---AST parameter
>     P3---Access mode to deliver AST (maximized with caller's access mode)"
> 
> Note the description of P1, to wit: "... 0 if the corresponding AST is disabled". Admittedly, the English could be better ("is disabled" would probably be better described as "is to be disabled.").
> 
> - Bob Gezelter, http://www.rlgsc.com
I tried this:

           sts = sys$qiow (     ,
        1                       %val(chn),
        1                       %val(IO$_SETMODE.or.IO$M_CTRLYAST),
        1                       iosb,,,%VAL(0),,,,,)

but it does not disable the AST.  What am I missing?