Penny know PLC indirect addressing and direct addressing

Direct addressing

points out that the exact operation instruction address directly. For example A Q10. 0, for instructions A Q10. 0 is the direct manipulation of address.

therefore, relative, indirect addressing the indirect points out instructions the exact address. For example, A Q [ MD10] , the address is not directly given here, but indirectly through MD10 this memory address.

the types of indirect addressing

indirect addressing can be divided into two types: memory indirect addressing and register indirect addressing. As shown in figure 1. Figure 1

memory addressing way indirect addressing

memory indirect addressing the address of a given format is: + pointer address identifier. Pointer indicates the value contained in the storage unit, by numerical unit is the exact address.

memory indirect addressing format is divided into two kinds of Pointers:

16 pointer:

16 address pointer for the timer, counter, block ( DB、FC、神奇动物) Addressing, 16 pointer is regarded as an unsigned integer ( 0 - 65535). It said the timer ( T) And counter ( C) And data blocks ( DB、DI) Or block ( FB, FC) Number of 16 bit pointer format is as follows:

figure 2 16 pointer format

32-bit pointer:

32-bit address pointer is used to I, Q, M, L, a block of data bits, bytes, characters, such as storage and double word addressing, 32-bit address pointer can use a double word, said a 0 ~ 2 a as an address of addressing operation, 3rd to 18th as addressable byte address operation, 19th ~ 31 is not defined, 32-bit pointer format is as follows:

figure 3 32-bit pointer format

register indirect addressing

register indirect addressing to pass the CPU address register AR1, AR2 addressing. AR1, AR2 are 32-bit registers, register indirect addressing only use 32-bit pointer.

is divided into internal addressing regional indirect addressing and cross area. Internal area register indirect addressing

pointer format same as a pointer to a 32-bit memory indirect addressing, a 0 ~ 2 a as an address of addressing operation, 3rd to 18th as addressable byte address operation, 19th ~ 31 is not defined, 32-bit pointer format is as follows:

figure 4 internal regional 32-bit pointer

cross regional register indirect addressing

contains a pointer to the memory area information, called cross region pointer. Similarly, cross area by 32-bit pointer, register indirect addressing to use address register AR1 or AR2. 32-bit pointer, cross area left 0 ~ 18 format is the same as the inner regions of the 32-bit Pointers, 19 ~ 23, 27 ~ 20 undefined, 31 for cross region pointer identifier. 24 ~ 26 is a storage area address identifier, 8 said 8 kinds of storage area: 000 indicates no address area, such as P# 12. 0; 001 said I input the address area, such as P# I12. 0; Q 010 said output address area, such as P# Q12. 0; M. 011, says mark address area, such as P# M12. 0; 100 said data blocks ( DB) The data, such as P# DB1. DBX12. 0101 said data blocks ( DI) The data, such as P# DI1. DIX12. 0110 L said area address area, such as P# L12. 0; 111 said call V block area address area, such as P# V12. 0; Cross region POINTER format is as follows:

P# POINTER and ANY POINTER

P# POINTER to POINTER is a kind of used to pass a POINTER parameter according to the type, the length is 6 bytes. Used to be called the function of the FC and function block of FB transfer compound data types ( Such as ARRAY, STRUCT and DT, etc. ) The argument. In the called function FC and FB internal function blocks to indirect access to the argument of the memory.

figure 6 P# POINTER

ANY POINTER POINTER is a kind of used to pass a POINTER parameter according to the type, can be seen as an extension of POINTER type, a POINTER type to complex, length of 10 bytes, add 2 bytes, maximum byte ( 字节0) The second byte (fixed for B# 16 # 10, 字节1) As ANY the data type of the pointer points to area, and the next two bytes ( 字节3、4) Combination for an INT, the length of the area for ANY Pointers, known as the coefficient of repeated Repetition factor) 。 The remaining six byte function the same as the POINTER type. Format is as follows:

figure 7 ANY pointer