NXP Semiconductors freescale K51 Series Reference Manual

Table 2-4. Memories and memory interfaces (continued)Module DescriptionSRAM Internal system RAM. Partial SRAM kept powered in VLLS2 low leakage mode.SRAM controller Manages simultaneous accesses to system RAM by multiple master peripheralsand core.System register file 32-byte register file that is accessible during all power modes and is powered byVDD.VBAT register file 32-byte register file that is accessible during all power modes and is powered byVBAT.Serial programming interface (EzPort) Same serial interface as, and subset of, the command set used by industry-standard SPI flash memories. Provides the ability to read, erase, and programflash memory and reset command to boot the system after flash programming.2.3.4 ClocksThe following clock modules are available on this device.Table 2-5. Clock modulesModule DescriptionMulti-clock generator (MCG) The MCG provides several clock sources for the MCU that include:• Phase-locked loop (PLL) — Voltage-controlled oscillator (VCO)• Frequency-locked loop (FLL) — Digitally-controlled oscillator (DCO)• Internal reference clocks — Can be used as a clock source for other on-chipperipheralsSystem oscillator The system oscillator, in conjunction with an external crystal or resonator,generates a reference clock for the MCU.Real-time clock oscillator The RTC oscillator has an independent power supply and supports a 32 kHzcrystal oscillator to feed the RTC clock. Optionally, the RTC oscillator can replacethe system oscillator as the main oscillator source.2.3.5 Security and Integrity modulesThe following security and integrity modules are available on this device:Table 2-6. Security and integrity modulesModule DescriptionCyclic Redundancy Check (CRC) Hardware CRC generator circuit using 16/32-bit shift register. Error detection forall single, double, odd, and most multi-bit errors, programmable initial seed value,and optional feature to transpose input data and CRC result via transpose register.Chapter 2 IntroductionK51 Sub-Family Reference Manual, Rev. 6, Nov 2011Freescale Semiconductor, Inc. 59