General purpose timers (GPTs) in SPEAr3xx

AN3140

4/14

Doc ID 16997 Rev 1

The SPEAr3xx GPTs always generate precise alarm interrupts, for example in the case of a

system tick for a RTOS. Nevertheless, as you can see in Section 2: Reading a free-running

timer counter, GPTs can return unpredictable read values when they are running and the

input clock is asynchronous (or not in phase).

Table 2.

GPTx clock source selector

Register

Address

Value

GPT1

PRPH_CLK_CFG [08]

0xFCA8_0028 (bit8)

0: PLL3 48 MHz

GPT2

PRPH_CLK_CFG[11]

0xFCA8_0028 (bit11)

0: PLL3 48 MHz

GPT3

PRPH_CLK_CFG[12]

0xFCA8_0028 (bit12)

0: PLL3 48 MHz