# Real Time Timer Controller Interface Peripheral

RTTC (AT91S_RTTC) 0xFFFFFD20 (AT91C_BASE_RTTC)

## RTTC Software API (AT91S_RTTC)

Offset | Field | Description
0x0 | RTTC_RTMR (SYSC_RTMR) | Real-time Mode Register
0x4 | RTTC_RTAR (SYSC_RTAR) | Real-time Alarm Register
0x8 | RTTC_RTVR (SYSC_RTVR) | Real-time Value Register
0xC | RTTC_RTSR (SYSC_RTSR) | Real-time Status Register

## RTTC Register Description

#### RTTC: AT91_REG SYSC_RTMR Real-time Mode Register

- RTTC AT91C_RTTC_RTMR 0xFFFFFD20

Offset | Name | Description
15..0 | SYSC_RTPRES AT91C_SYSC_RTPRES | Real-time Timer Prescaler Value Defines the number of SLCK periods required to increment the Real-time Timer. The maximum period is obtained by programming RTPRES to 0x0 corresponding to 65536 Slow Clock cycles.
16 | SYSC_ALMIEN AT91C_SYSC_ALMIEN | Alarm Interrupt Enable 0 = The bit ALMS in SYSC_RTSR has no effect on SCIRQ. 1 = The bit ALMS in SYSC_RTSR asserts SCIRQ.
17 | SYSC_RTTINCIEN AT91C_SYSC_RTTINCIEN | Real Time Timer Increment Interrupt Enable 0 = The bit RTTINC in SYSC_RTSR has no effect on SCIRQ. 1 = The bit RTTINC in SYSC_RTSR asserts SCIRQ.
18 | SYSC_RTTRST AT91C_SYSC_RTTRST | Real Time Timer Restart 0 = No effect. 1 = Reloads and restarts the clock divider with the new programmed value. This also resets the 32-bit counter.

#### RTTC: AT91_REG SYSC_RTAR Real-time Alarm Register

- RTTC AT91C_RTTC_RTAR 0xFFFFFD24

Offset | Name | Description
31..0 | SYSC_ALMV AT91C_SYSC_ALMV | Alarm Value Defines the Alarm value compared with the Real-time Timer.

#### RTTC: AT91_REG SYSC_RTVR Real-time Value Register

- RTTC AT91C_RTTC_RTVR 0xFFFFFD28

Offset | Name | Description
31..0 | SYSC_CRTV AT91C_SYSC_CRTV | Current Real-time Value Returns the current value of the Real-time Timer.

#### RTTC: AT91_REG SYSC_RTSR Real-time Status Register

- RTTC AT91C_RTTC_RTSR 0xFFFFFD2C

Offset | Name | Description
0 | SYSC_ALMS AT91C_SYSC_ALMS | Real-time Alarm Status 0 = The Real-time Alarm has not occured since the last read of SYSC_RTSR. 1 = The Real-time Alarm occured since the last read of SYSC_RTSR.
1 | SYSC_RTTINC AT91C_SYSC_RTTINC | Real-time Timer Increment 0 = The Real-time Timer has not been incremented since the last read of SYSC_RTSR. 1 = The Real-time Timer has been incremented since the last read of SYSC_RTSR.