RTC0ADR = 0x5; // CAPTURE5 Target the capture registers
RTC0ADR |= 0x80;
while ((RTC0ADR & 0x80) == 0x80); // Poll on the BUSY bit
s_counts_temp.byte[0] = RTC0DAT;

RTC0ADR = 0x4; // CAPTURE4 Target the capture registers
RTC0ADR |= 0x80;
while ((RTC0ADR & 0x80) == 0x80); // Poll on the BUSY bit
s_counts_temp.byte[1] = RTC0DAT;

RTC0ADR = 0x3; // CAPTURE3 Target the capture registers
RTC0ADR |= 0x80;
while ((RTC0ADR & 0x80) == 0x80); // Poll on the BUSY bit
s_counts_temp.byte[2] = RTC0DAT;

RTC0ADR = 0x2; // CAPTURE2 Target the capture registers
RTC0ADR |= 0x80;
while ((RTC0ADR & 0x80) == 0x80); // Poll on the BUSY bit
s_counts_temp.byte[3] = RTC0DAT;

RTC0ADR = 0x1; // CAPTURE1 Target the capture registers
RTC0ADR |= 0x80;
while ((RTC0ADR & 0x80) == 0x80); // Poll on the BUSY bit
s_counts_temp.byte[4] = RTC0DAT;

this is too little information. Which device are you using? How do you initialize RTC? ...

Regards,

Scotty

LONG RTC_Read(void){
s_counts_temp.l = 0;
while ((RTC0ADR & 0x80) == 0x80); // Poll on the BUSY bit
RTC0ADR &= 0xF0;
RTC0ADR |= 0x06;

RTC0DAT = 0xD9; // Initiate the transfer to the CAPTUREn
// registers

while ((RTC0ADR & 0x80) == 0x80); // Poll on the BUSY bit

I use c8051F410
Okay, now I have a datasheet to work with

Initialization is IMHO OK
Sometimes this is the error But I assume it's really okay...

Please, advice for any type of MCU.
Only possible if any CPU uses the same RTC peripheral. If any CPU means any F41x device, then the peripheral is the same.

I read seconds. But fail to get proper data from CAPTURE0 and CAPTURE1.
Hm... I'm not sure if I understand your RTC_Read() function, for me it doesn't do what the name says... If I'd to read the capture register, my first try would look like this (not tested):

LONG RTC_Read(void){
  while(RTC0ADR & 0x80 == 0x80); // Poll on the busy flag
  RTC0ADR &= 0xF0;
  RTC0ADR |= 0x06;               // set address for RTC control register
  RTC0DAT = RTC0DAT | 0x01;      // initiate transfer to capture registers
  while(1) {
    RTC0ADR |= 0x80;             // initiate indirect data transfer
    while(RTC0ADR & 0x80 == 0x80); // Poll on the busy flag
    if(RTC0DAT & 0x01 == 0)        // check if transfer is complete
      break;
  }
  RTC0ADR &= 0xF0;
  RTC0ADR |= 0x00;               // set address for Capture0 register
  RTC0ADR |= 0x80;               // initiate indirect data transfer
  while(RTC0ADR & 0x80 == 0x80); // Poll on the busy flag
  ucBCap0 = RTC0DAT;             // read content of Capture0 register
  RTC0ADR &= 0xF0;
  RTC0ADR |= 0x01;               // set address for Capture1 register
  RTC0ADR |= 0x80;               // initiate indirect data transfer
  while(RTC0ADR & 0x80 == 0x80); // Poll on the busy flag
  ucBCap0 = RTC0DAT;             // read content of Capture1 register
  RTC0ADR &= 0xF0;
  RTC0ADR |= 0x02;               // set address for Capture2 register
  RTC0ADR |= 0x80;               // initiate indirect data transfer
  while(RTC0ADR & 0x80 == 0x80); // Poll on the busy flag
  ucBCap0 = RTC0DAT;             // read content of Capture2 register
  RTC0ADR &= 0xF0;
  RTC0ADR |= 0x03;               // set address for Capture3 register
  RTC0ADR |= 0x80;               // initiate indirect data transfer
  while(RTC0ADR & 0x80 == 0x80); // Poll on the busy flag
  ucBCap0 = RTC0DAT;             // read content of Capture3 register
  RTC0ADR &= 0xF0;
  RTC0ADR |= 0x04;               // set address for Capture4 register
  RTC0ADR |= 0x80;               // initiate indirect data transfer
  while(RTC0ADR & 0x80 == 0x80); // Poll on the busy flag
  ucBCap0 = RTC0DAT;             // read content of Capture4 register
  RTC0ADR &= 0xF0;
  RTC0ADR |= 0x05;               // set address for Capture5 register
  RTC0ADR |= 0x80;               // initiate indirect data transfer
  while(RTC0ADR & 0x80 == 0x80); // Poll on the busy flag
  ucBCap0 = RTC0DAT;             // read content of Capture5 register
  
  // put in code for needed modifications for return value
}

Note that according to datasheet setting the register adresses in RTC0ADR is not neccessary since the addresses will increment automatically when accessing the capture registers.
And from my understanding of the RTC module, you cannot read seconds, minutes, etc. directly, instead you have to calculate them by yourself...

Regards,

Scotty

[This message has been edited by Scotty (edited August 15, 2010).]