Register Notation And Register Numbers; General-Purpose Registers - Epson S1C33 Series Core Manual

2.9 Register Notation and Register Numbers

The following describes the register notation and register numbers in the C33 PE Core instruction set.
In the instruction code, a register is specified using a 4-bit field, with the register number entered in that field. In the
mnemonic, a register is specified by prefixing the register name with "%."

2.9.1 General-Purpose Registers

rs is a metasymbol indicating the general-purpose register that holds the source data to be operated on or
%rs
transferred. The register is actually written as %r0, %r1, ... or %r15.
rd is a metasymbol indicating the general-purpose register that is the destination in which the result of
%rd
operation is to be stored or data is to be loaded. The register is actually written as %r0, %r1, ... or %r15.
rb is a metasymbol indicating the general-purpose register that holds the base address of memory to be
%rb
accessed. In this case, the general-purpose registers serve as an index register. The register is actually
written as [%r0], [%r1], ... or [%r15], with each register name enclosed in brackets "[]" to denote
register indirect addressing. In register indirect addressing, the post-increment function provided for
continuous memory addresses can be used. In such a case, the register name is suffixed by "+," as in [%r0]+.
When post-increment is specified, each time memory is accessed, the base address is incremented by an
amount equal to the accessed size.
rb is also used as a symbol indicating the register that contains the jump address for the call or jp
instruction. In this case, the brackets "[]" are unnecessary, and the register is written as %r0, %r1, ... or
%r15.
The bit field that specifies a register in the instruction code contains the code corresponding to a given register
number. The relationship between the general-purpose registers and the register numbers is listed in the table below.
General-purpose register
S1C33 FAMILY C33 PE CORE MANUAL
Table 2.9.1.1 General-Purpose Registers
Register number
R0 0
R1 1
R2 2
R3 3
R4 4
R5 5
R6 6
R7 7
R8 8
R9 9
R10 10
R11 11
R12 12
R13 13
R14 14
R15 15
EPSON
Register notation
%r0
%r1
%r2
%r3
%r4
%r5
%r6
%r7
%r8
%r9
%r10
%r11
%r12
%r13
%r14
%r15
2 REGISTERS
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