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HT95C40P Datasheet(PDF) 17 Page - Holtek Semiconductor Inc |
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HT95C40P Datasheet(HTML) 17 Page - Holtek Semiconductor Inc |
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17 / 51 page  HT95CXXX Rev. 1.50 17 May 26, 2005 When in the Idle mode, the 32768Hz stops, the WDT stops counting and lose its protecting purpose. In this situation the logic can only be re-started by external logic. The high nibble and bit3 of the WDTS are reserved for user defined flags, which can be used to indicate some specified status. The WDT time-out under Normal mode or Green mode will initialize ²chip reset² and set the status bit ²TO². But in the Sleep mode or Idle mode, the time-out will initial- ize a ²warm reset² and only the program counter and stack pointer are reset to 0. To clear the WDT contents (including the WDT prescaler), three methods are adopted; external reset (a low level to RES pin), soft- ware instruction and a ²HALT² instruction. The software instruction include ²CLR WDT² and the other set ²CLR WDT1² and ²CLR WDT2². Of these two types of instruction, only one can be active depending on the mask option ²WDT instr².Ifthe ²CLR WDT² is se- lected (i.e. One clear instruction), any execution of the CLR WDT instruction will clear the WDT. In the case that ²CLR WDT1² and ²CLR WDT2² are chosen (i.e. Two clear instructions), these two instructions must be exe- cuted to clear the WDT; otherwise, the WDT may reset the chip as a result of time-out. Controller Operation Mode Holtek ¢s telephone controllers support two system clock and four operation modes. The system clock could be 32768Hz or 3.58MHz and operation mode could be Nor- mal, Green, Sleep or Idle mode. These are all selected by the software. The following conditions will force the operation mode to change to Green mode: · Any reset condition from any operation mode · Any interrupt from Sleep mode or Idle mode · Port A wake-up from Sleep mode or Idle mode How to change the Operation Mode · Normal mode to Green mode: Clear MODE1 to 0, then operation mode is changed to Green mode but the UPEN status is not changed. However, UPEN can be cleared by software. Bit No. Label R/W Function 0 1 2 WS0 WS1 WS2 RW Watchdog Timer division ratio selection bits Bit 2, 1, 0=000, Division ratio=1:1 Bit 2, 1, 0=001, Division ratio=1:2 Bit 2, 1, 0=010, Division ratio=1:4 Bit 2, 1, 0=011, Division ratio=1:8 Bit 2, 1, 0=100, Division ratio=1:16 Bit 2, 1, 0=101, Division ratio=1:32 Bit 2, 1, 0=110, Division ratio=1:64 Bit 2, 1, 0=111, Division ratio=1:128 7~3 ¾ RW Unused bit. These bits are read/write-able. WDTS (09H) Register Bit No. Label R/W Function 4~0 ¾ RO Unused bit, read as ²0² 5 UPEN RW 1: Enable frequency up conversion function to generate 3.58MHz 0: Disable frequency up conversion function to generate 3.58MHz 6 MODE0 RW 1: Disable 32768Hz oscillator while the HALT instruction is executed (Idle mode) 0: Enable 32768Hz oscillator while the HALT instruction is executed (Sleep mode) 7 MODE1 RW 1: Select 3.58MHz as CPU system clock 0: Select 32768Hz as CPU system clock MODE (26H) Register Operation Mode Description HALT Instruction MODE1 MODE0 UPEN Operation Mode 32768Hz 3.58MHz System Clock Not execute 1 X 1 Normal ON ON 3.58MHz Not execute 0 X 0 Green ON OFF 32768Hz Be executed 0 0 0 Sleep ON OFF HALT Be executed 0 1 0 Idle OFF OFF HALT Note: ²X² means don¢t care |
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