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RX Voltage Detection Circuit (LVD) and Power-On Reset (POR) Renesas Electronics America Inc. Ver. 1.00 © 2011 Renesas Electronics America Inc. All rights reserved. Course Introduction Purpose Learn RX reset sources & voltage detection Content Voltage Detection Circuit (LVD) LVD Control & Status Registers RX Reset Sources Determining Reset Source Learning Time 20 Minutes 2 © 2011 Renesas Electronics America Inc. All rights reserved. RX Voltage Detection Circuit (LVD) Monitors Vcc voltage level Interrupt and/or reset at two fixed voltages: Vdet1 & Vdet2 Off at power up by default Key code register protects against unwanted modification Vcc Vdet2 Vdet1 VPOR Reset 3 © 2011 Renesas Electronics America Inc. All rights reserved. LVD Key Code Register LVD Key Code Register (LVDKEYR) Enables writing to LVD Control Register (LVDCR) Write 0x3C to enable writing Other values lock out changes Locked on reset LVD Key Code Register (LVDKEYR) After reset 4 b7 b6 b5 b4 b3 b2 b1 b0 0 0 0 0 0 0 0 0 © 2011 Renesas Electronics America Inc. All rights reserved. Low-Voltage Detection Control Register LVD Control Register (LVDCR) LVD1E, LVD2E – Enable bits for LVD1 and LVD2 (1 = enabled) LVD1RI, LV2RI – Selects interrupt or reset generation for each – 0=Reset, 1=Interrupt Interrupts are NMI’s (set NMIER.LVDEN in the ICU) LVD1 and LVD2 are locked & disabled after reset Lock it after changes with LVDKEYR! LVD Control Register (LVDCR) After reset 5 b7 b6 b5 b4 b3 b2 b1 b0 LVD2E LVD2RI --- --- LVD1E LVD1RI --- --- 0 0 0 0 0 0 0 0 © 2011 Renesas Electronics America Inc. All rights reserved. Reset Status Register Reset Status Register (RSTR) LVD1F, LVD2F – Indicate state of LVD1 and LVD2 (1=detected) PORF – 0=Reset caused by something other than POR – 1=POR was detected DPSRSTF – Indicates reason for exit from deep software stby mode Reset Status Register (RSTR) After reset 6 b7 b6 b5 b4 b3 b2 b1 b0 DPSRSTF --- --- --- --- LVD2F LVD1F PORF 0 0 0 0 0 0 0 0 © 2011 Renesas Electronics America Inc. All rights reserved. RX Resets 7 Power-on reset Pin reset Voltage-monitoring Deep software standby reset Independent watchdog timer Watchdog timer © 2011 Renesas Electronics America Inc. All rights reserved. Power-on reset 8 Generated internally RES# pin high when power is applied VCC rises above VPOR (2.58V typ.) Power-on reset time (tPOR) of 20-50ms (35 ms typ.) RSTSR.PORF = 1 Don’t place capacitor on RES# line! © 2011 Renesas Electronics America Inc. All rights reserved. Pin Reset Drive RES# low tRESW: Hold RES# low for the longer of: 20 tcyc 1.5 uS All reset-related status registers are cleared 9 © 2011 Renesas Electronics America Inc. All rights reserved. Voltage-Monitoring Reset Internally generated by LVD Caused by VCC < Vdet1 or VCC < Vdet2 Internal reset starts tdet (max 200uS) after VCC falls Rising edge on VCC tVOFF (min 200uS) after falling edge Power-on reset time (tPOR) of 20-50ms (35 typ.) starts after rising edge RSTSR.LVDnF = 1 (n=1 or 2) 10 © 2011 Renesas Electronics America Inc. All rights reserved. Deep Software Standby Reset Generated when deep software stdby exited by interrupt Startup delay specified in DPSWCR.WTSTS[5:0] RSTSR.DPSRSTF = 1 11 © 2011 Renesas Electronics America Inc. All rights reserved. Watchdog Resets Independent Watchdog (IWDT) Clock source = OCOCLK IWDTSR.UNDFF indicates timeout/reset Watchdog Timer (WDT) Clock source = PCLK / divisor RSTCSR.WOVF indicates timeout/reset Also drives WDT# pin (do NOT connect to RST# pin!) 12 © 2011 Renesas Electronics America Inc. All rights reserved. Determining Reset Source 13 © 2011 Renesas Electronics America Inc. All rights reserved. Summary RX Voltage Detection Circuit (LVD) LVD Control & Status Registers RX Power-On Reset (POR) Other RX Reset Sources Determining Reset Source Thank you! 14 © 2011 Renesas Electronics America Inc. All rights reserved. PROPERTIES On passing, 'Finish' button: On failing, 'Finish' button: Allow user to leave quiz: User may view slides after quiz: User may attempt quiz: Goes to Next Slide Goes to Next Slide At any time At any time Unlimited times Thank You Renesas Electronics America Inc. © 2011 Renesas Electronics America Inc. All rights reserved.