EF6805P2 datasheet(21/31 Pages) STMICROELECTRONICS

21 / 31 page

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.

EF6805U3

21/31

EF6805P2 Datasheet(PDF) 21 Page - STMicroelectronics