Table 3-3. Access Types - Intel i960 Jx Developer's Manual

PROGRAMMING ENVIRONMENT
Access Type
R Read
Read
RO
Only
W Write
R/W Read/Write ld, st, and sysctl instructions are allowed access.
Write
WwG when
Granted
sysctl
Read
Sysctl-RwG
when
Granted
atmod
AtMod
update
3-8

Table 3-3. Access Types

Description
Read (ld instruction) accesses are allowed.
Only Read (ld instruction) accesses are allowed. Write (st
instruction) accesses are ignored.
Write (st instruction) accesses allowed.
Writing or Modifying (through a st or sysctl instruction) the register
is only allowed when modification-rights to the register have been
granted. An OPERATION.UNIMPLEMENTED fault occurs when an
attempt is made to write the register before rights are granted. See
section 9.2.7.2, "Hardware Breakpoints" (pg. 9-5)
getting modification rights to breakpoint registers.
The value of the register can only be read by executing a sysctl
instruction issued with the modify memory-mapped register
message type. Modification rights to the register must be granted
first or an OPERATION.UNIMPLEMENTED fault occurs when the
sysctl is executed. A ld instruction to the register returns unpre-
dictable results.
Register can be updated quickly through the atmod instruction. The
atmod ensures correct operation by performing the update of the
register in an atomic manner which provides synchronization with
previous and subsequent operations. This is a faster update
mechanism than sysctl and is optimized for a few special registers.
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