Show the Status of CY, AC and P flag after the addition of 88 H and 93 H in the given instruction

#education #highereducation #academic #microcontroller #statusofflag #auxiliaryFlag

To determine the status of the Carry (CY), Auxiliary Carry (AC), and Parity (P) flags after the addition of 88H and 93H, we need to perform the addition and then analyze the result according to the flag rules of an 8-bit microprocessor (such as the 8085).

Let's proceed step-by-step:

1. **Perform the addition of 88H and 93H:**

```
88H = 1000 1000B
93H = 1001 0011B
----------------
1 0001 1011B
```

The binary addition of 88H and 93H results in 1 0001 1011B. Since this is a 9-bit result, the carry-out is 1, and the lower 8 bits of the result are 0001 1011B, which is 1BH in hexadecimal.

2. **Determine the status of the Carry (CY) flag:**

The Carry flag is set if there is a carry-out from the most significant bit (MSB). In this case, there is a carry-out (the 9th bit is 1), so the Carry flag (CY) is set.

3. **Determine the status of the Auxiliary Carry (AC) flag:**

The Auxiliary Carry flag is set if there is a carry from the lower nibble (the lower 4 bits) to the upper nibble (the upper 4 bits) during addition. Let's look at the addition of the lower and upper nibbles separately:

Lower nibbles:
```
1000 (8H)
0011 (3H)
------
1011 (BH)
```

Upper nibbles:
```
1000 (8H)
1001 (9H)
------
10001 (11H, with carry)
```

Since there is a carry from the lower nibble to the upper nibble (from 1000 + 0011 = 1011), the Auxiliary Carry flag (AC) is set.

4. **Determine the status of the Parity (P) flag:**

The Parity flag is set if the number of 1s in the result (excluding the carry-out) is even. The result of the addition is 0001 1011B. Counting the number of 1s:

```
0001 1011B has 4 ones.
```

Since 4 is an even number, the Parity flag (P) is set.

**Summary of flag status after adding 88H and 93H:**
- Carry (CY): Set (1)
- Auxiliary Carry (AC): Set (1)
- Parity (P): Set (1)

So, the final statuses of the flags are:
- CY = 1
- AC = 1
- P = 1

[Fawaz-Ansari]

Sir could you please explain this, how to write the program.

Q2.Write an assembly language program for the 8051 to transfer the message “HAPPY
NEW YEAR” serially at a baud rate of 9600 in mode 1. Assume the 8051 is operating
on 11.0592 MHz.