how to read register address

Projects Programming
1

I am reading a register map for a UART and the base memory mapped address for the UART is 0x00021000. I've created a pointer to this address as:

#define UART_BASE 0x00021000
volatile uint32_t *uart = (volatile uint32_t*) UART_BASE;

The register map is attached and the status register is offset by 2. What would be the address of the status register?

#define UART_STATUS 0x00021000
volatile uint32_t *uart = (volatile uint32_t*) UART_STATUS

This for an arduino project that I'm porting to another (more difficult) MCU.

Thanks

uart_reg.png
uart_reg.png1191×425 85 KB

2

What would be the address of the status map?

I do not know what you mean by "status map". There is a status register, at UART_BASE+2.

3

sorry that was a typo fixed now.

4

uint32_t is 32 bits, so wouldn't it just be uart+1? (that is incrementing the base by 32 bits, 16 bits for rx, 16 bits for tx).

5

Hi tammytam,

Thanks, but if UART base is at 0x00021000 how can you calculate the address of the status register only? I suppose that is my question, sorry. It is 0x00021000 + ? = status register address.

Thanks

6

0x00021004

That is if you are addressing bytes. Or do it from the base pointer like I put:

volatile uint32_t *uart = (volatile uint32_t*) UART_BASE;
volatile uint32_t *status = uart+1;

I think :wink:

7

sorry if this is a really stupid question but how did you calculate 0x00021004?

8

4 bytes offset from the base, 2 bytes (16 bit) for the RX, 2 bytes (16 bit) for the TX. Should place you at the start of the status register.

9

ah got you now! thanks

10

Why are you using a 32 bit pointer to point to 16 bit data? Life would be so much simpler if you used a pointer that was the same size as the data you are pointing to.

Then, the offset would be 2.