APPENDIX A MIPS III INSTRUCTION SET DETAILS
Preliminary User’s Manual S15543EJ1V0UM 433
(1) Instruction notation examples
The following examples illustrate the application of some of the instruction notation conventions:
Example 1:
GPR [rt] ← immediate || 016
Sixteen zero bits are concatenated with an immediate value (typically 16 bits), and the 32-bit string is
assigned to general register
rt
.
Example 2:
(immediate15)16 || immediate15...0
Bit 15 (the sign bit) of an immediate value is extended for 16-bit positions, and the result is concatenated
with bits 15 through 0 of the immediate value to form a 32-bit sign extended value.
A.2 Load and Store Instructions
In the VR4120A CPU implementation, the instruction immediately following a load may use the loaded contents of
the register. In such cases, the hardware interlocks, requiring additional real cycles, so scheduling load delay slots is
still desirable, although not required for functional code.
In the load and store descriptions, the functions listed in Table A-2 are used to summarize the handling of virtual
addresses and physical memory.
Table A-2. Load and Store Common Functions
Function Description
AddressTranslation Uses the TLB to find the physical address given the virtual address. The function fails and an exception
is taken if the required translation is not present in the TLB.
LoadMemory Uses the cache and main memory to find the contents of the word containing the specified physical
address. The low-order three bits of the address and the Access Type field indicate which of each of the
four bytes within the data word need to be returned. If the cache is enabled for this access, the entire
word is returned and loaded into the cache. If the specified data is short of word length, the data position
to which the contents of the specified data is stored is determined considering the endian mode and
reverse endian mode.
StoreMemory Uses the cache, write buffer, and main memory to store the word or part of word specified as data in the
word containing the specified physical address. The low-order three bits of the address and the Access
Type field indicate which of each of the four bytes within the data word should be stored. If the specified
data is short of word length, the data position to which the contents of the specified data is stored is
determined considering the endian mode and reverse endian mode.