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GMS81C2112 Datasheet(PDF) 80 Page - Hynix Semiconductor |
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GMS81C2112 Datasheet(HTML) 80 Page - Hynix Semiconductor |
80 / 107 page ![]() GMS81C2112/GMS81C2120 74 JUNE. 2001 Ver 1.00 17.2 Stop Mode In the Stop mode, the on-chip oscillator is stopped. With the clock frozen, all functions are stopped, but the on-chip RAM and Control registers are held. The port pins out the values held by their respective port data register, port di- rection registers. Oscillator stops and the systems internal operations are all held up. • The states of the RAM, registers, and latches valid immediately before the system is put in the STOP state are all held. • The program counter stop the address of the instruction to be executed after the instruction "STOP" which starts the STOP operating mode. The Stop mode is activated by execution of STOP in- struction after clearing the bit WAKEUP of CKCTLR to “0”. (This register should be written by byte opera- tion. If this register is set by bit manipulation instruc- tion, for example "set1" or "clr1" instruction, it may be undesired operation) In the Stop mode of operation, VDD can be reduced to min- imize power consumption. Care must be taken, however, to ensure that VDD is not reduced before the Stop mode is invoked, and that VDD is restored to its normal operating level, before the Stop mode is terminated. The reset should not be activated before VDD is restored to its normal operating level, and must be held active long enough to allow the oscillator to restart and stabilize. Note: After STOP instruction, at least two or more NOP in- struction should be written Ex) LDM CKCTLR,#0000_1110B STOP NOP NOP In the STOP operation, the dissipation of the power asso- ciated with the oscillator and the internal hardware is low- ered; however, the power dissipation associated with the pin interface (depending on the external circuitry and pro- gram) is not directly determined by the hardware operation of the STOP feature. This point should be little current flows when the input level is stable at the power voltage level (VDD/VSS); however, when the input level gets high- er than the power voltage level (by approximately 0.3 to 0.5V), a current begins to flow. Therefore, if cutting off the output transistor at an I/O port puts the pin signal into the high-impedance state, a current flow across the ports input transistor, requiring to fix the level by pull-up or other means. Release the STOP mode The exit from STOP mode is hardware reset or external in- terrupt. Reset re-defines all the Control registers but does not change the on-chip RAM. External interrupts allow both on-chip RAM and Control registers to retain their val- ues. If I-flag = 1, the normal interrupt response takes place. If I- flag = 0, the chip will resume execution starting with the instruction following the STOP instruction. It will not vec- tor to interrupt service routine. (refer to Figure 17-1) When exit from Stop mode by external interrupt, enough oscillation stabilization time is required to normal opera- tion. Figure 17-2 shows the timing diagram. When release the Stop mode, the Basic interval timer is activated on wake-up. It is increased from 00H until FFH. The count overflow is set to start normal operation. Therefore, before STOP instruction, user must be set its relevant prescaler di- vide ratio to have long enough time (more than 20msec). This guarantees that oscillator has started and stabilized. By reset, exit from Stop mode is shown in Figure . Figure 17-1 STOP Releasing Flow by Interrupts IEXX =0 =1 STOP INSTRUCTION STOP Mode Interrupt Request STOP Mode Release I-FLAG =1 Interrupt Service Routine Next INSTRUCTION =0 Master Interrupt Enable Bit PSW[2] Corresponding Interrupt Enable Bit (IENH, IENL) |