SWCU195A December 2024 – May 2025 CC2744R7-Q1 , CC2745P10-Q1 , CC2745R10-Q1 , CC2745R7-Q1 , CC2755R10
The VGM module monitors the VDDD supply rail for any positive or negative glitches, which means detection of overshoot or undershoot conditions and triggers a device reset. It detects transients or glitches on the VDDD supply pin at the rate of 100 MV/s to 2 GV/s, and it detects glitches with a minimum width of 1-2ns. When the VGM module is enabled, it is ready for operation in a maximum of 70μs.
The VGM digital logic and configuration bits are implemented in SYS0 and PMCTL modules. The VGMCFG register in SYS0 contains two separate bits to disable the undershoot detector and overshoot detector. The reset value of these two disable bits is 0, so that both the detector circuits in VGM are enabled once the VDDD domain is powered and comes out of reset to start device boot up.
The VGM module remains enabled after boot up, so the user application can take advantage of this module if useful for the application, else the individual detectors of VGM can be disabled through the VGMCFG register. Both of the VGM detectors can be individually disabled and re-enabled by software at a later point if needed. VGM detectors will be automatically enabled by hardware upon power cycle or shutdown exit or any of the other chip reset conditions. The outputs from the undershoot and overshoot detectors are combined (logical OR) inside the VGM analog module to generate a reset request output. When VGM is enabled, it always triggers a device reset when it detects a glitch on VDDD, and this reset can not be masked.
When VGM undershoot and/or overshoot detectors are kept enabled by the user application, then they are disabled during standby entry and are automatically re-enabled by hardware upon wake-up. There is no need for VGM operation in standby as the VDDD supply is turned off. The VGM enable qualifier signal from the PMCTL is used inside the SYS0 module to override the VGM enables during standby entry. VGM module is disabled by hardware and is not operational in shutdown mode.
VGM enable status is signaled by SYS0 to PMCTL based on USHTDETDIS and OSHTDETDIS bits in the VGMCFG register. When VGM is disabled, PMCTL does not delay the SVT reset release. When VGM is enabled, PMCTL checks the value of the user policy bit in its MMR. If the value is 0 (default case) it will wait for the VGM ready signal to get asserted by VGM analog. VGM ready is asserted by VGM analog to PMCTL once it fully settles, and it may take up to 70us maximum. VGM reset request output will be gated within VGM analog until it fully settles, and VGM ready is generated. Once PMCTL observes VGM ready getting set, it releases SVT reset. When the user policy bit is programmed to a value of 1, PMCTL does not wait for VGM ready from VGM analog and proceeds with SVT reset release.
VGM will be enabled by default, so PMCTL will always delay SVT reset release until VGM ready is received, and this will be the behavior for cold power up, pin reset, internal chip resets, and shutdown exit. The user needs to program the policy bit value to 1 in PMCTL if no impact to standby wake latency (~40us) is desired; else the policy bit default value of 0 will impact the standby latency by up to a maximum of ~70μs. Since the user policy bit is implemented in PMCTL MMR it is retained during standby, and the setting takes effect during standby exit operation. Refer to the device-specific data sheet for standby exit latencies for both values of the PMCTL policy bit when VGM is enabled.
Refer to SYS0 chapter for VGMCFG MMR description of VGM module.