Apple Lisa - Page 63

Confidential
Lisa Hardware Reference Manual
7-Jul-81
Privilege violation
The 68000 has two states of privilege, User and Supervisor.
Certain instructions (RESET, for example) can occur only
in superv~sor state. An attempt to execute a priviliged
instruction from user state causes a privilege violation
interrupt to be generated.
PROM Programmable Read Only Memory
RAM Random Access Memory (actually ROM is also random access
memory-RAM, however, is read/write memory).
ROM Read Only Memory.
RS232-C A communication protocol.
RWTS Read/Write/Track/Sector. The controlling routines that,
drive the floppy disk controller both on the Lisa and the
Apple II.
Segment A segment is an independent address space. It may have
little obvious relation to physical memory.
Shift register A register is a device which can store information. A
shift register is able to shift all its bits left or
right.
SSP
Supervisor Stack Pointer. See Privilege Violation.
Synchronous modem'
Synchronous transmission puts the framing information
around a group of characters. The transmitter then
automatically inserts fill characters into the stream
whenever necessary to maintain synchronicity. Because
more
of the bits are data (there are fewer stop and
start bits than in asynchronous transmission), data
transfers can go at a faster rate.
tristate A logic output that can be inactive, high or low. The
three states are, therefore, active high, active low,
and open.
us
Word
ZIF
micro-second. The letter 'u' is used because it looks
like the small Greek letter mu (small Roman 'm' is used
for milli, and large Roman 'M' is used for Mega).
A group of
bytes. On the Lisa, a word is usually 16
bits, or two bytes. Long Words are 32 bits or four
bytes.
Zero Insertion Force
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