On Tue, 3 Dec 2013 21:54:00 -0600, Robert A. Rosenberg <[email protected]> 
wrote:

>Definitely a large positive number over 2^16-1 (so there is something
>other than zeros in the high 2 bytes).
>
>The low 2 bytes have to be between x"0000" and x"0008" to pass the CH
>R1,=H8" check.
>
>As to negative numbers, that number also has to be within certain
>boundaries so the low bytes meet the same range check.
>
>
>At 12:59 -0600 on 12/03/2013, Ray Overby wrote about Re:
>Un-authorized caller calling authorized services.:
>

I'm not sure what you are saying there. 

CH does not ignore the high order bytes of the register - in effect it 
sign-extendeds the halfword (H'8' there) to a fullword for comparison with the 
register. The problem is with negative function codes, not "large" positive 
ones. 

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