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EM6520 Datasheet(PDF) 6 Page - EM Microelectronic - MARIN SA |
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EM6520 Datasheet(HTML) 6 Page - EM Microelectronic - MARIN SA |
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6 / 55 page 
EM6520 03/02 REV. D/449 Copyright 2002, EM Microelectronic-Marin SA 6 www.emmicroelectronic.com 2 Operating modes The EM6520 has two low power dissipation modes, standby and sleep. Figure 4 is a transition diagram for these modes. 2.1 ACTIVE Mode The active mode is the actual CPU running mode. Instructions are read from the internal ROM and executed by the CPU. Leaving the active mode: via the halt instruction to go into standby mode, writing the SLEEP bit to go into Sleep mode or detecting the reset condition from port A to go into reset mode. 2.2 STANDBY Mode Executing a HALT instruction puts the EM6520 into standby mode. The voltage regulator, oscillator, watchdog timer, LCD, interrupts, timers and counters are operating. However, the CPU stops since the clock related to instruction execution stops. Registers, RAM and I/O pins retain their states prior to STANDBY mode. STANDBY is canceled by a RESET or an Interrupt request if enabled. 2.3 SLEEP Mode Writing to the Sleep bit in the RegSysCntl1 register puts the EM6520 in sleep mode. The oscillator stops and most functions of the EM6520 are inactive. To be able to write to the Sleep bit, the SleepEn bit in RegSysCntl2 must first be set to "1". In SLEEP mode only the voltage regulator is active to maintain the RAM data integrity, all other functions are in reset state. SLEEP mode may be canceled only by the input reset combination from port A . Due to the cold-start characteristics of the oscillator, waking up from sleep mode may take some time to guarantee stable oscillation. During sleep mode and the following start up the EM6520 is in reset state. Waking up from sleep mode clears the Sleep flag but not the SleepEn bit. Inspecting the SleepEn allows to determine if the EM6520 was powered up (SleepEn = "0") or woken from sleep mode (SleepEn = "1"). TAKE CARE !!! To quit sleep mode, one must be sure to have a suitable defined combination of port A inputs for reset (see section 4.2). The Bit NoInpReset has no action during sleep mode. Table 2.3.1 Shows the state of the EM6520 functions in STANDBY and SLEEP modes FUNCTION STANDBY SLEEP Oscillator Active Stopped Oscillator supervisor Active Stopped Instruction execution Stopped Stopped Interrupt functions Active Stopped Registers and flags Retained Reset RAM data Retained Retained Option registers Retained Retained Timer/Counter's Active Reset Logic watchdog Active Reset I/O port B Active High Impedance, Pull resistors as defined Input port A Active NoInputRes = "0" for reset generation Only active for Reset generation NoInputRes = "X" LCD Active Stopped (display off) Voltage Level Detector finishes on going measure, then stop Stopped Figure 4 Mode transition diagram Active Halt instruction Sleep bit write IRQ Standby Sleep Reset=1 Reset=0 Reset=1 Reset=1 Reset |
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