TC1796
System Units (Vol. 1 of 2)
System Control Unit
User’s Manual
5-3
V2.0, 2007-07
SCU, V2.0
The Power Management State Machine (PMSM) controls the power management mode
of all system components during Run Mode, Idle Mode, and Sleep Mode. The PMSM
continues to operate in Idle Mode and Sleep Mode, even if all other system components
have been disabled, so that it can reawaken the system as needed. This flexibility in
power management provides minimum power consumption for any application.
Besides these explicit software-controlled power-saving modes, in the TC1796 special
attention has been paid to automatic power-saving in those operating units which are
currently not required or idle. In that case they are shut off automatically until their
operation is required again.
In typical operation, Idle Mode and Sleep Mode may be entered and exited frequently
during the run time of an application. For example, system software will typically cause
the CPU to enter Idle Mode each time it has to wait for an interrupt before continuing its
tasks. In Sleep Mode and Idle Mode, wake-up is performed automatically when any
enabled interrupt signal is detected, or if the Watchdog Timer signals the CPU an NMI
trap.
5.1.2
Power Management Control and Status Register, PMG_CSR
The set of registers used for power management is divided between central TC1796
components and peripheral components. The PMG_CSR register provides software
control and status information for the PMSM. There are individual clock control registers
for peripheral components because the Sleep Mode behavior of each peripheral
component is programmable. When entering Idle Mode and Sleep Mode, the PMSM
directly controls TC1796 components such as the CPU, but indirectly controls peripheral
components through their clock control registers.