Epson S1C63000 - Manual (Page 41)

S1C63000 CORE CPU MANUAL EPSON 35
CHAPTER 4: INSTRUCTION SET
These instructions perform a PC relative branch using the content (4 bits) of a memory specified
with the [addr6] as a relative address. The branch destination address is [the address next to the
branch instruction] + [the contents (0 to 15) of the memory specified with the addr6].
(2) Instructions that access from FFC0H to FFFFH
This area is reserved for the I/O memory in the S1C63 Family and the following instructions are
provided to operate the control bits of the peripheral circuits.
An address within FFC0H to FFFFH is specified with the addr6. However the addr6 is handled as
0 to 3FH in the machine codes.
CLR [addr6],imm2 ...Clears a bit specified with the imm2 in a memory specified with the addr6
SET [addr6],imm2 ...Sets a bit specified with the imm2 in a memory specified with the addr6
TST [addr6],imm2 ...Tests a bit specified with the imm2 in a memory specified with the addr6
Write only or read only control bits may have been assigned depending on the peripheral circuit.
Pay attention when using the above-mentioned instructions for such bits or addresses containing
such bits.
• Signed 8-bit PC relative addressing
The signed 8-bit PC relative addressing is the addressing mode used for the branch instructions. The
signed 8-bit relative address (-128 to 127) that is specified in the operand is added to the address next
to the branch instruction to branch to that address.
The following instructions operate in this addressing mode.
Jump instructions: JR sign8
JRC sign8
JRNC sign8
JRZ sign8
JRNZ sign8
Call instruction: CALR sign8
4.1.2 Extended addressing mode
In the S1C63000, when data is written to the EXT register (the E flag is set) and a specific instruction
follows, the data specified by that instruction is extended with the EXT register data (see Section 2.1.5).
When the E flag is set, instructions are extended in an addressing mode different from the mode that is
specified in each instruction. This is the extended addressing mode that will be explained below.
However, instructions that can operate in the extended addressing mode are limited to those indicated in
the instruction list, so check it when programming.
Further the extended addressing mode is effective only for the instruction following immediately after
writing data to the EXT register and setting the E flag to "1" (the E flag is reset to "0" by executing that
instruction). When using an instruction in the extended addressing mode, write data to be extended to
the EXT register or set the E flag (when the E register has already been set).
• 16-bit immediate data addressing
The addressing mode of the following instructions, which have an 8-bit immediate data as the
operand, change to the 16-bit immediate data addressing when the E flag is set to "1". Consequently, it
is possible to transfer and operate a 16-bit immediate data to the X or Y register.
Instructions that operate in the 16-bit immediate data addressing mode with the E flag
LDB %XL,imm8 LDB %Y,imm8
ADD %X,sign8 ADD %Y,sign8
CMP %X,imm8 CMP %X,imm8
The data is extended into 16 bits in which the E register data is the high-order 8 bits and the immedi-
ate data specified with the above instruction is the low-order 8 bit.