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The PICE pseudo-variable PCHECK determines whether the PICE system operates with
80286 protection checking on or off. The default for PCHECK is TRUE.
PCHECK = TRUE
PCHECK = FALSE
Real Mode and PCHECK
When the 8086 is in real mode and PCHECK is TRUE, you can neither display nor alter the
segment caches, the LDTR, the GDTR, the TR, and the IDTR. When the 8086 is in real mode
and PCHECK is FALSE, you can display and alter the segment caches, the LDTR, the GDTR,
the TR, and the IDTR.
Protected Mode and PCHECK
When the user program executes in protected mode and PCHECK is FALSE, the PICE system
ignores the 80286 protection rules when loading the 80286 registers and accessing memory.
You can display and alter the segment caches, the LDTR, the GDTR, the TR, and the IDTR.
When the user program executes in protected mode and PCHECK is TRUE, the PICE system
obeys the 80286 protection rules when loading the 80286 registers. You can display but not
alter the segment caches, the LDTR, the GDTR, the TR, and the IDTR. You must use a virtual
address to access memory. The PICE system obeys the 80286 protection rules.
For more information on address protection and PCHECK, see the Address protection and
PCHECK entries in the PICE™ System Reference Manual.
Memory Mapping for the 80286 Probe
The PICE system with an 80286 probe supports the standard PICE memory mapping features
plus the GRANULARITY pseudo-variable.
With the 8086/8088 and the 80186/80188 probes, you must map HS and MB memory in
blocks of IK bytes. If you try to map a block of less than IK bytes, the PICE system rounds up
to the nearest lK-byte block and prints a message telling you that it rounded the value. With the
80286 probe, however, you can map 1024 blocks of memory in either IK blocks or 16K
blocks. When GRANULARITY = IK, the upper four address bits are ignored by mapping
logic; thus, only the lower megabyte of memory is mappable. When GRANULARITY =
16K, the entire address space is available. Choose the block size by setting the GRANULAR
ITY pseudo-variable. To change the granularity, you must have all program memory mapped to
either USER or GUARDED.
The PICE system always maps OHS memory in blocks of 16K, even if GRANULARITY
is IK.
4-18
the PICE system observes the 80286 protection rules when view
ing and modifying 80286 registers and accepting memory
addresses.
the PICE system ignores the 80286 protection rules as much as
possible.
The PICE™ System Personality Modules (Probes)
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