Maxim-integrated Secure Microcontroller Manual do Utilizador Página 62

  • Descarregar
  • Adicionar aos meus manuais
  • Imprimir
Vista de página 61
Secure Microcontroller User’s Guide
62 of 187
7. POWER MANAGEMENT
All secure microcontrollers are implemented using CMOS circuitry for low power consumption. Two
software-initiated modes are available for further power saving at times when processing is not required
and V
CC
is at normal operating voltage. These are the idle and stop modes. The additional third mode is
the data retention or zero-power state, which is made possible by the on-chip circuitry. The control and
status bits that apply to these operating modes are contained in the PCON register and are summarized in
Control/Status Bits for Power Control. In addition, Table 7-A summarizes the state of external pins in
each of these modes.
7.1 Idle Mode
Idle mode suspends activity of the CPU but allows the timer/counters, I/O pins, and serial port to continue
their operation. This greatly reduces the number of switching nodes and thereby dramatically reduces the
total power consumption of the device. Idle mode is useful for applications in which lower power
consumption is desired with fast response to external interrupts but no other processing.
Software invokes idle mode by setting the IDL bit (PCON.0) to a logic 1. The instruction that sets this bit
is the last instruction executed before idle mode operation begins. Once in idle mode, the microprocessor
preserves the entire CPU status including the stack pointer, program counter, program status word,
accumulator, and RAM. There are two ways to terminate the idle mode. The first is from an interrupt that
has been previously enabled prior to entering idle mode. This will clear the IDL bit and cause the CPU to
enter the interrupt service routine as normal. When the RETI instruction is executed, the next instruction
that is executed is the one that immediately follows the instruction that set the IDL bit.
The second method of terminating the idle mode is by a reset. At this time the IDL bit is cleared and the
CPU is placed in the reset state. Since the clock oscillator continues to run in the idle mode, an oscillator
startup delay (referred to as t
POR
in the AC Electrical Specifications in the data sheet) is not generated
following the reset. Two machine cycles are required to complete the reset operation (24 oscillator
periods). It should be noted that the watchdog timer continues to run during idle and that a reset from the
on-chip watchdog timer terminates idle mode.
Vista de página 61
1 2 ... 57 58 59 60 61 62 63 64 65 66 67 ... 186 187

Comentários a estes Manuais

Sem comentários

CoolBox manuales

La lista de dispositivos de CoolBox contiene 5 manuales de usuario y guías para 5 modelos en 5 tipo de dispositivos

Ratones
Modelos Tipo de documento
Fobos Guía de usuario    CoolBox Fobos, 1 paginas
Auriculares para móvil
Modelos Tipo de documento
H309 Manual de usuario   CoolBox H309, 12 paginas
H2 Manual de usuario   CoolBox H2, 1 paginas
Bocinas Portables
Modelos Tipo de documento
X3M Manual   CoolBox X3M, 1 paginas
Los teléfonos inteligentes
Modelos Tipo de documento
QUORE V57 Manual   CoolBox QUORE V57 4GB White, 11 paginas