Maxim-integrated MAXQ622 Uživatelský manuál stáhnout pdf (Strana 9)

MAXQ612/MAXQ622 User’s Guide

Maxim Integrated 2-5

The MAXQ instruction set is designed to be highly orthogonal. All arithmetic and logical operations that use two reg-

isters can use any register along with the accumulator. Data can be transferred between any two registers in a single

instruction.

2.2 Register Space

The MAXQ612/MAXQ622 provide a total of 16 register modules. Each of these modules contains 32 registers. The first

eight registers in each module can be read from or written to in a single cycle; the second eight registers can be read

from in a single cycle and written to in two cycles (by using the prefix register, PFX[n]); the last 16 registers can be

read or written in two cycles (always requiring use of the prefix register, PFX[n]).

Registers can be either 8 or 16 bits in length. Within a register, any number of bits can be implemented; bits not

implemented are fixed at zero. Data transfers between registers of different sizes are handled as shown in Table 2-1.

• If the source and destination registers are both 8 bits wide, data is transferred bit to bit accordingly.

• If the source register is 8 bits wide and the destination register is 16 bits wide, the data from the source register is

transferred into the lower 8 bits of the destination register. The upper 8 bits of the destination register are set to the

current value of the prefix register; this value is normally zero, but it can be set to a different value by the previous

instruction if needed. The prefix register reverts back to zero after one cycle, so this must be done by the instruction

immediately before the one that would be using the value.

• If the source register is 16 bits wide and the destination register is 8 bits wide, the lower 8 bits of the source are

transferred to the destination register.

• If both registers are 16 bits wide, data is copied bit to bit.

The above rules apply to all data movements between defined registers. Data transfer to/from undefined register loca-

tions has the following behavior:

• If the destination is an undefined register, the MOVE is a dummy operation, but can trigger an underlying operation

according to the source register (e.g., @DP[n]--).

• If the destination is a defined register and the source is undefined, the source data for the transfer depends upon the

source module width. If the source is from a module containing 8-bit or 8-bit and 16-bit source registers, the source

data is equal to the prefix data concatenated with 00h. If the source is from a module containing only 16-bit source

registers, 0000h source data is used for the transfer.

The 16 available register modules are broken up into two different groups. The low six modules (specifiers 0h to5h) are

known as the peripheral register modules, while the high 10 modules (specifiers 6h to 0Fh) are known as the system

groups from a programming perspective.

The system registers define basic functionality that remains the same across all products based on the MAXQ612/

MAXQ622 architecture. This includes all register locations that are used to implement higher level op codes as well as

the following common system features:

• ALU (16 bits) and associated status flags (zero, equals, carry, sign, overflow)

• 16 working accumulator registers (16-bit width), along with associated control registers

• Instruction pointer

• Registers for interrupt control and handling

• Autodecrementing loop counters for fast, compact looping

• Two data pointer registers, a frame pointer, and a stack pointer for data memory/stack access

• One code pointer register for program memory access

The peripheral registers define additional functionality included in the MAXQ612/MAXQ622. This functionality is broken

up into discrete modules so that only the features that are required for a given product need to be included. Because

the peripheral registers add functionality outside the common MAXQ system architecture, they are not used to imple-

ment op codes.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 254 255

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