ZiLOG System 8000 Hardware Reference Manual

HRM 2110g
HRM
4.9.6. System Segments and Protection: Logic on the CPU
board partitions segments into system segments (logical seg-
ments 0, 1, 64 and 65), and user segments (logical segments
2 to 63 and 66 to 127). Any reference to a system segment
always enables the System Break Register for comparison with
the logical address offset, while any reference to a user
segment always enables the Normal Break Register. These
comparisons are independent of whether the 28001 CPU is exe-
cuting in system or normal mode. The function of the system
segment detection logic is to prohibit normal mode programs
from accessing system mode segments. Normal mode references
to system segments are not valid and cause no MMU to be
selected, and a segment violation forced upon the CPU. This
violation is maintained until cleared by the segment trap
acknowledge status of the CPU.
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ZiLOG System 8000 Specifications

General

Brand	ZiLOG
Model	System 8000
Category	Desktop
Language	English