37. Construct UART Data Frame with Parity Bit

You are implementing UART data transmission logic. A control register configures parity settings for data framing. The control register is defined as an 8-bit register:
 

typedef struct {
    uint8_t parity_enable : 1;   // 0 = Disabled, 1 = Enabled
    uint8_t parity_type   : 1;   // 0 = Even parity, 1 = Odd parity
    uint8_t reserved      : 6;   // Reserved bits
} UART_Control;

You’re given a 7-bit data (0–127). Your task is to create an 8-bit UART frame using the control register:

• If parity is disabled, the MSB (bit 7) is 0, and the remaining 7 bits are data.
• If parity is enabled:
  • Count the number of 1s in the 7-bit data.
  • Add a parity bit at the MSB (bit 7):
    • Even parity ➝ parity bit = 0 if 1s are even, 1 if odd.
    • Odd parity ➝ parity bit = 0 if 1s are odd, 0 if even.

Parity in Simple Terms

Parity is an error-detection bit added to the data:

• Even parity → total number of 1s (including parity) must be even
  (e.g., data = 1011 → has 3 ones → parity = 1 → 10001011)
   
• Odd parity  → total number of 1s (including parity) must be odd
  (e.g., data = 1010 → has 2 ones → parity = 1 → 10001010)
  
   

Example-1

Input: data = 85, parity_enable = 1, parity_type = 0
Output: frame = 0x55

Example-2

Input: data = 3, parity_enable = 1, parity_type = 1
Output: frame = 0x83

Example-3

Input: data = 25, parity_enable = 0, parity_type = 0
Output: frame = 0x19