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the rate of a standard 8051 device). It employs a pipelined architecture that greatly increases its instruction
throughput over the standard 8051 architecture. The instruction timing is different than that of the standard
8051.
In many 8051 implementations, a distinction is made between machine cycles and clock cycles, with
machine cycles varying from 2 to 12 clock cycles in length. However, the 1T-80C51 implementation is based
solely on clock cycle timing. All instruction timings are specified in terms of clock cycles. For more detailed
information about the 1T-80
C51 instructions, please refer section “34 Instruction Set” which includes the
mnemonic, number of bytes, and number of clock cycles for each instruction.
5.3
CPU Addressing Mode
5.3.1
Direct Addressing (DIR)
In direct addressing the operand is specified by an 8-bit address field in the instruction. Only internal data
RAM and SFRs can be direct addressed.
5.3.2
Indirect Addressing (IND)
In indirect addressing the instruction specified a register which contains the address of the operand. Both
internal and external RAM can be indirectly addressed. The address register for 8-bit addresses can be R0 or
R1 of the selected bank, or the Stack Pointer. The address register for 16-bit addresses can only be the 16-bit
data pointer register
– DPTR.
5.3.3
Register Instruction (REG)
The register banks, containing registers R0 through R7, can be accessed by certain instructions which
carry a 3-bit register specification within the op-code of the instruction. Instructions that access the registers
this way are code efficient because this mode eliminates the need of an extra address byte. When such
instruction is executed, one of the eight registers in the selected bank is accessed.
5.3.4
Register-Specific Instruction
Some instructions are specific to a certain register. For example, some instructions always operate on the
accumulator or data pointer, etc. No address byte is needed for such instructions. The op-code itself does it.
5.3.5
Immediate Constant (IMM)
The value of a constant can follow the op-code in the program memory.
5.3.6
Index Addressing
Only program memory can be accessed with indexed addressing and it can only be read. This
addressing mode is intended for reading look-up tables in program memory. A 16-bit base register (either
DPTR or PC) points to the base of the table, and the accumulator is set up with the table entry number.
Another type of indexed addressing is used in the conditional jump instruction.
In conditional jump, the destination address is computed as the sum of the base pointer and the
accumulator.
Содержание CMT2380F17
Страница 27: ...CMT2380F17 Rev0 1 27 347 www cmostek com 1 25 Phase Noise...
Страница 111: ...CMT2380F17 Rev0 1 111 347 www cmostek com INT2IS 1 0 Selected Port Pin of nINT2 00 P4 4 01 P3 0 10 P1 1 11 P1 6...
Страница 131: ...CMT2380F17 Rev0 1 131 347 www cmostek com Figure 16 1 Timer 0 Mode 0 Structure Figure15 2 Timer 1 Mode 0 Structure...
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