SST89C54 datasheet(35/50 Pages) SST

35 / 50 page

344-2 8/00

FlashFlex51 MCU

SST89C54 / SST89C58

Preliminary Specifications

POWER-SAVING MODES

The SST89C54/58 provides three power saving modes

of operation for applications where power consumption

is critical. The three power saving modes are: Idle, Power

Down and Standby (Stop Clock).

Idle

Idle mode is entered by a software command which sets

the IDL bit in the PCON register. In Idle mode the

program counter (PC) is stopped. The system clock

continues to run and all interrupts and peripheral func-

tions (timers/counters, serial port, etc.) are active. In this

mode the power dissipation is approximately 25% of the

fully active device.

The SST89C54/58 exits Idle mode through either a

system interrupt or a hardware reset. The interrupt clears

the IDL bit and the program resumes execution begin-

ning at the instruction immediately following the one

which invoked the Idle mode. A hardware reset starts the

device similar to power-on reset.

FIGURE 20: POWER-ON RESET CIRCUIT

Power Down

The Power Down mode is also entered by a software

command which sets the PD bit in the PCON register. In

Power Down mode, the clock is stopped and external

interrupts are active for level sensitive interrupt only.

Power Down mode reduces the current dissipation to

15µA, typical.

The SST89C54/58 exits Power Down mode through

either an enabled external level sensitive interrupt or a

hardware reset. The interrupt clears the PD bit and the

program resumes execution beginning at the instruction

immediately following the one which invoked the Power

Down mode. A hardware reset starts the device similar

to power-on reset.

Standby (Stop Clock)

Standby mode is similar to Power Down mode, except

that Power Down mode is initiated by a software com-

mand and Standby mode is initiated by external hard-

ware gating off the external clock to the SST89C54/58

device. The current dissipation is reduced to 15µA,

typical. The on-chip SRAM and SFR data are maintained

in Standby mode. The device resumes operation at the

next instruction when the clock is reapplied to the part.

Table 10 outlines the different power-saving modes,

including entry and exit procedures and MCU

functionality.

344 ILL F31.1

VDD

10µF

8.2K

SST89C54/58

RST

XTAL2

XTAL1

12MHz

SST89C54 Datasheet(PDF) 35 Page - Silicon Storage Technology, Inc

SST89C54 Datasheet(HTML) 35 Page - Silicon Storage Technology, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

Datasheet Download

Link URL