ZiLOG System 8000 User Manual page 61

USER
51
system mode
termination
trap
Zilog
USER
A Running-state mode in which the SiN
flag in the FCW is 1 and the NIS line is
Low. In this mode, the CPU may exercise
privileged instructions.
When a command being executed finishes,
it is said to terminate. Commands nor-
mally terminate when they read an end-
of-file from their standard input.
A condition that occurs at the end of ar.
instruction that caused an illegal
operation. The
zaooo
traps are internal
traps arising from system call; unimple-
mented instruction and privileged
instructions executed in normal mode,
and an external trap, the segmentation
trap, arising from memory access viola-
tions in systems with memory management.
A
t~ap is similar to an interrupt in
that it causes the executing program
Status registers to be saved on the sys-
tem stack. Traps cannot be disabled.
vectored interrupts
Interrupts which use the identifier word
as a vector to _the interrupt service
routine. May be disabled.
word Two contiguous bytes (16 bits) starting
on an even addressable byte boundary.
Bits are numbered from the right, 0
through 15.
A
word is identified by the
address of the byte containing the most
significant bit, bit 15.
word register A 16-bit register.
working directory
ZEUS
Any directory a user is currently work-
ing in is called a working directory.
ZEUS
is the operating system for the
S8000 system.
Zilog
51