Coma FW-C2800 User's Guide download pdf (Page 174)

Timers, Interrupts, and the System Clock

Thread Scheduling 4-69

When the CLK Manager is enabled on the C6000 platform, the timer counter

enabled on the C5400 platform, the timer counter is decremented at the

following rate, where CLKOUT is the DSP clock speed in MIPS (see the

Global Settings Property dialog in the TMS320 DSP/BIOS API Reference

Guide for your platform) and TDDR is the value of the timer divide-down

When this register reaches 0 on the C5400 and C2800 platform, or the value

set for the period register on the C6000 platform, the counter is reset. On the

C5400 and C2800, it is reset to the value in the period register. On the C6000,

it is reset to 0. At this point, a timer interrupt occurs. When a timer interrupt

occurs, the HWI object for the selected timer runs the CLK_F_isr function,

which causes these events to occur:

❏ The low-resolution time is incremented by 1 on the C6000, C2800, and

C5000 platforms.

❏ All the functions specified by CLK objects are performed in sequence in

the context of that ISR.

Therefore, the low-resolution clock ticks at the timer interrupt rate and the

clock’s time is equal to the number of timer interrupts that have occurred. To

obtain the low-resolution time, you can call CLK_getltime from your

application code.

The CLK functions performed when a timer interrupt occurs are performed in

the context of the hardware interrupt that caused the system clock to tick.

Therefore, the amount of processing performed within CLK functions should

be minimized and these functions can invoke only DSP/BIOS calls that are

allowable from within an HWI.

Note:

CLK functions should not call HWI_enter and HWI_exit as these are called

internally when DSP/BIOS runs CLK_F_isr. Additionally, CLK functions

should not use the interrupt keyword or the INTERRUPT pragma in C

functions.

CLKOUT / (TDDR + 1)

1 2 ... 169 170 171 172 173 174 175 176 177 178 179 ... 275 276

No comments

Coma FW-C2800 User's Guide Page 174