# SAM3S8 RTT

## Real-time Timer (RTT) User Interface

### Registers

Register Mapping
Address | Register | Name | Access | Reset
--- | --- | --- | --- | ---
0x400E1430 | Mode Register | RTT_MR | read-write | 0x00008000
0x400E1434 | Alarm Register | RTT_AR | read-write | 0xFFFFFFFF
0x400E1438 | Value Register | RTT_VR | read-only | 0x00000000
0x400E143C | Status Register | RTT_SR | read-only | 0x00000000

### Register Fields

#### RTT Mode Register

Name: RTT_MR

Access: read-write

Address: 0x400E1430

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24
- | - | - | - | - | - | - | RTC1HZ
23 | 22 | 21 | 20 | 19 | 18 | 17 | 16
- | - | - | RTTDIS | - | RTTRST | RTTINCIEN | ALMIEN
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8
RTPRES
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
RTPRES

- RTPRES: Real-time Timer Prescaler Value

-

- ALMIEN: Alarm Interrupt Enable

  Value | Name | Description
  --- | --- | ---
  0 | - | The bit ALMS in RTT_SR has no effect on interrupt.
  1 | - | The bit ALMS in RTT_SR asserts interrupt.

- RTTINCIEN: Real-time Timer Increment Interrupt Enable

  Value | Name | Description
  --- | --- | ---
  0 | - | The bit RTTINC in RTT_SR has no effect on interrupt.
  1 | - | The bit RTTINC in RTT_SR asserts interrupt.

- RTTRST: Real-time Timer Restart

  Value | Name | Description
  --- | --- | ---
  0 | - | No effect.
  1 | - | Reloads and restarts the clock divider with the new programmed value. This also resets the 32-bit counter.

- RTTDIS: Real-time Timer Disable

  Value | Name | Description
  --- | --- | ---
  0 | - | The real-time timer is enabled.
  1 | - | The real-time timer is disabled (no dynamic power consumption).

- RTC1HZ: Real-Time Clock 1Hz Clock Selection

  Value | Name | Description
  --- | --- | ---
  0 | - | The RTT 32-bit counter is driven by the 16-bit prescaler roll-over events.
  1 | - | The RTT 32-bit counter is driven by the RTC 1 Hz clock.

#### RTT Alarm Register

Name: RTT_AR

Access: read-write

Address: 0x400E1434

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24
ALMV
23 | 22 | 21 | 20 | 19 | 18 | 17 | 16
ALMV
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8
ALMV
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
ALMV

- ALMV: Alarm Value

-

#### RTT Value Register

Name: RTT_VR

Access: read-only

Address: 0x400E1438

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24
CRTV
23 | 22 | 21 | 20 | 19 | 18 | 17 | 16
CRTV
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8
CRTV
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
CRTV

- CRTV: Current Real-time Value

-

#### RTT Status Register

Name: RTT_SR

Access: read-only

Address: 0x400E143C

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24
- | - | - | - | - | - | - | -
23 | 22 | 21 | 20 | 19 | 18 | 17 | 16
- | - | - | - | - | - | - | -
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8
- | - | - | - | - | - | - | -
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
- | - | - | - | - | - | RTTINC | ALMS

- ALMS: Real-time Alarm Status

  Value | Name | Description
  --- | --- | ---
  0 | - | The Real-time Alarm has not occurred since the last read of RTT_SR.
  1 | - | The Real-time Alarm occurred since the last read of RTT_SR.

- RTTINC: Real-time Timer Increment

  Value | Name | Description
  --- | --- | ---
  0 | - | The Real-time Timer has not been incremented since the last read of the RTT_SR.
  1 | - | The Real-time Timer has been incremented since the last read of the RTT_SR.