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FDC37C78-HT Datasheet(PDF) 58 Page - Microchip Technology |
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FDC37C78-HT Datasheet(HTML) 58 Page - Microchip Technology |
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58 / 82 page  58 AUTO POWER MANAGEMENT Power management capabilities are provided for the floppy disk. Two types of power management are provided; direct powerdown and auto powerdown. Direct powerdown is controlled by the powerdown bit in the configuration registers. Auto Powerdown can be enabled by setting the Auto Powerdown Enable bit in the configluation registers. FDC Power Management Direct power management is controlled by bit 3 of Configuration Register 0(CR0). Refer to CR0 bit 3 for more information. Auto Power Management is enabled by CR7 bit 7. When set, this bit allows FDC to enter powerdown when all of the following conditions have been met: 1. The motor enable pins of register DOR are inactive (zero). 2. The part must be idle; MSR=80H and INT = 0 (INT may be high even if MSR = 80H due to polling interrupts). 3. The internal head unload timer must have expired. 4. The Auto powerdown timer (10msec) must have timed out. An internal timer is initiated as soon as the auto powerdown command is enabled. The part is then powered down when all the conditions are met. During the countdown of the powerdown timer, any operation of read MSR or read/write data (FIFO) will reinitiate the timer. Disabling the auto powerdown mode cancels the timer and holds the FDC37C78 out of auto powerdown. DSR From Powerdown If DSR powerdown is used when the part is in auto powerdown, the DSR powerdown will override the auto powerdown. However, when the part is awakened from DSR powerdown, the auto powerdown will once again become effective. Wake Up From Auto Powerdown If the part enters the powerdown state through the auto powerdown mode, then the part can be awakened by reset or by appropriate access to certain registers. If a hardware or software reset is used then the part will go through the normal reset sequence. If the access is through the selected registers, then the FDC37C78 resumes operation as though it was never in powerdown. Besides activating the RESET pin or one of the software reset bits in the DOR or DSR, the following register accesses will wake up the part: 1. Enabling any one of the motor enable bits in the DOR register (reading the DOR does not awaken the part). 2. A read from the MSR register. 3. A read or write to the Data register. |
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Similar Description - FDC37C78-HT |
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