EF6805U3 Datasheet, PDF (21/31 Pages) STMicroelectronics – 8-BIT MICROCOMPUTER UNIT

EF6805U3
modify or test its contents, and write the modified va-
lue back to memory or to the register. The test for
negative or zero (TST) instruction is included in
read-modify-write instructions through it does not
perform the write. Rfer to table 2.
Caution
The corresponding DDRs for ports A, B, and C
are write-only registers (registers at $004, $005,
and $006). A read operation on these registers
is undefined. Since BSET and BCLR are read-
modify-write functions, they cannot be used to
set or clear a DDR bit (all ”unaffected” bits would
be set). It is recommended that all DDR bits in a
port be written using a single-store instruction.
BRANCH INSTRUCTIONS - The branch instruc-
tions cause a branch from the program when a cer-
tain condition is met. Refer to table 3.
BIT MANIPULATION INSTRUCTIONS - These ins-
tructions are used on any bit in the first 256 bytes of
the memory. One group either sets or clears. The o-
ther group performs the bit test branch operations.
Refer to table 4.
Caution
The corresponding DDRs for ports A, B, and C
are write-only registers (registers at $004, $005,
and $006). A read operation on these registers
is undefined. Since BSET and BCLR are read-
modify-write functions, they cannot be used to
set or clear a DDR bit (all ”unaffected” bits would
be set). It is recommended that all DDR bits in a
port be written using a single-store instruction.
CONTROL INSTRUCTIONS - The control instruc-
tions control the MCU operations during program
execution. Refer to table 5.
ALPHABETICAL LISTING - The complete instruc-
tion set is given in alphabetical order in table 6.
OPCODE MAP SUMMARY - Table 7 is an opcode
map for the instructions used on the MCU.
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