JAJSHM4U April 2001 – July 2019 TMS320F2810 , TMS320F2811 , TMS320F2812
PRODUCTION DATA.
デバイスごとのパッケージ図は、PDF版データシートをご参照ください。
In PLL enabled mode, if the input clock XCLKIN or the oscillator clock is removed or absent, the PLL will still issue a “limp-mode” clock. The limp-mode clock will continue to clock the CPU and peripherals at a typical frequency of 1–4 MHz. The PLLCR register should have been written to with a non-zero value for this feature to work.
Normally, when the input clocks are present, the watchdog counter will decrement to initiate a watchdog reset or WDINT interrupt. However, when the external input clock fails, the watchdog counter will stop decrementing (that is, the watchdog counter does not change with the limp-mode clock). This condition could be used by the application firmware to detect the input clock failure and initiate necessary shut-down procedure for the system.
NOTE
Applications in which the correct CPU operating frequency is absolutely critical must implement a mechanism by which the DSP will be held in reset, should the input clocks ever fail. For example, an R-C circuit may be used to trigger the XRS pin of the DSP, should the capacitor ever get fully charged. An I/O pin may be used to discharge the capacitor on a periodic basis to prevent it from getting fully charged. Such a circuit would also help in detecting failure of the VDD3VFL rail.