11 lesson: single-chip calculation instruction

Single chip microcontroller without inlet position Add A, # data; example: add a, # 10h Add A, Direct; Example: Add A, 10h Add A, RN; Examples: Add A, R7 Add A, @ ri; example: add A, @ r0 Uses: Add the value of A with the value thereof, and final result is returned to A. Example: Mov A, # 30h Add A, # 10h Then the end of the article is executed, the value in A is 40h. The following topic exercises themselves Mov 34h, # 10h MOV R0, # 13h Mov A, 34H Add A, R0 Mov r1, # 34h Add A, @ r1 Brought in place AddC A, RN AddC A, Direct AddC a, @ ri AddC a, # data Uses: add the value of A and the value thereof, and plus the value in the inlet bits C. Description: Since the 51 single-chip microcomputer is an 8-bit machine, you can only do 8 mathematical operations, but the range of 8 operations is only 0-255, which is not enough in actual work, so it is necessary to expand, usually The 2 8-bit mathematics is combined to become a 16-bit operation, so that the range of the number that can be expressed can reach 0-65535. How to merge? In fact, it is very simple, let's take a 10-way number of routines: 66 + 78. These two numbers are added, we don't care about this process, but in fact, we do this: Do 6 + 8 (low) first, then do 6 + 7, this is a high level. I did two additions, but I didn't deliberately divide the addition to two additions, or we didn't realize that we did two additions. The reason why it is divided into two times is because these two numbers exceeded a number of dispensers (0-9). When you have a low position, we do it in your proper position when we do, and then you will add this. The same is true when you do 16 additions in your computer, first do 8 digits, if the two numbers are added, but also "click" to make a tag, this tag is the carry bits c, in the PSW. This C is added to the high addition. Example: 1067H + 10A0H, first do 67h + A0H = 107h, and 107h obviously exceeds 0FFH, so it is finally saved in A, and 1 to the CY bit in PSW, in other words, CY is equivalent to 100h. Then do 10 h + 10h + cyming, the result is 21h, so the final result is 2107h. Single-chip subtraction command with borrowing position Subb A, RN Subb A, Direct Subb A, @ ri Subb a, # data Set (each H, (R2) = 55H, CY = 1, after executing instructions Subb A, R2, the value in A is 73 h. Explanation: There is no single-chip subtraction command without borrowing, if you need to do a subtraction command (when doing the first time), you can clear CY. Multiplication Mul ab The function of this microcontroller command is to multiply the two 8-bit unsigned numbers in A and B, and the multi-multiplier results are generally large, so the final result is expressed in 1 16 digits, where high 8 bits are placed in B Medium, low 8 bits are placed in A. When the product is larger than fffffh (65535), 0V is set (overflow), otherwuit OV is 0, and CY is always 0. Example: (a) = 4Eh, (b) = 5dH, execution instruction After MUL AB, the product is 1 C56H, so it is 1Ch in B, and the A is placed 56h. Division directive Div AB The function of this microcontroller instruction is to use the 8-bit unsigned number in A, except for the 8-bit unsigned number (A / B). The division generally occurs, but it is possible to directly express the decimal in the computer. It is used by our primary school students. If the primary school students have not exposed to the decimal, such as 13/5, their merchants are 2, the remainder is 3. In addition to, the discharge is in A, the remainder is placed in B. CY and OV are 0. If the value in the first B in the first b is 00h, that is, the divisor is 0, then 0V = 1. Add 1 instruction INC A INC RN Inc Direct INC @RI Inc DPTR The use is very simple, that is, add the value in the rear target 1. Example: (a) = 12H, (R0) = 33h, (21H) = 32h, (34H) = 22 h, DPTR = 1234H. Execute the following instructions: INC A (a) = 13h INC R2 (R0) = 34h INC 21H (21H) = 33h INC @ r0 (34h) = 23h INC DPTR (DPTR) = 1235H The resulting results are as shown above. Description: From the results, INC A and Add A, # 1 are similar, but INC A is single byte, single cycle instruction, and add # 1 is double byte, double cycle instruction, and INC A does not affect PSW bit. , If (a) = 0ffh, after INC A (a) = 00h, CY remains unchanged. If it is Add A, # 1, (a) = 00h, and CY must be 1. Therefore, add 1 instructions are not suitable for adding, in fact it is mainly used to do counting, address increase, etc. In addition, the additional commands are all one of the cores of A. The calculation results must also be placed in A, while the objects of the 1 type of instructions are much wide, which can be registers, memory addresses, The address of the address, etc. 1 instruction 1 instruction Dec A Dec rn DIRECT Dec @RI Similar to plus 1 instruction, there is not much to say. Combined training: Mov A, # 12h MOV R0, # 24h Mov 21h, # 56h Add A, # 12h Mov dptr, # 4316h Add A, DPH Add A, R0 CLR C Subb A, DPL Subb A, # 25h INC A Setb C AddC a, 21h Inc R0 Subb A, R0 Mov 24h, # 16h CLR C Add A, @ r0 First, each step is written, and then the above topic is then built, and the changes in the software simulation, the register and the content of the relevant unit are observed, whether the same is the same as the own expected results. Read more