NonStop S-Series Server Description Manual (G06.27+)

Native Execution Mode
HP NonStop S-Series Server Description Manual—520331-004
7-7
Procedure Name Spaces for the System Library
results if needed, reverts to accelerated mode and the TNS stack, and returns control
to the TNS or accelerated code that called it.
In summary, referring to Figure 7-3: an XCAL instruction in TNS mode fetches the
XEP table entry for the target procedure. A DPCL instruction is presented with the
XEP entry as an argument. If CS = 1 in that entry, the shell map is consulted for the
starting address of the target RISC code, which may be an accelerated procedure in
SC or SL, or may be a to-RISC shell. An accelerated XCAL goes directly to the
accelerated code or shell. If the target procedure is CALLABLE, entry is through its
gateway.
Figure 7-3. Gateways and To-RISC Shells Enable TNS Access to System Library
TNS Name Space
TNS XCAL
DPCL
Accelerated XCAL
XEP
Entry
XEP
Table
CS =
1
0
Shell Map
Accelerated
Gateway
Accelerated
SC or SL
Procedure
Normal
TNS
Flow
Shell
Gateway
To-RISC
Shell
Native
Procedure
Native Name Space
VST313.vsd