2.2.3 Memories and Memory InterfacesThe following memories and memory interfaces are available on this device.Table 2-4. Memories and memory interfacesModule DescriptionFlash memory • Program flash memory — non-volatile flash memory that can executeprogram codeFlash memory controller Manages the interface between the device and the on-chip flash memory.SRAM Internal system RAM. Partial SRAM kept powered in LLS2 and VLLS2 low leakagemode.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.FlexBus External bus interface with multiple independent, user-programmable chip-selectsignals that can interface with external SRAM, PROM, EPROM, EEPROM, flash,and other peripherals via 8-, 16- and 32-bit port sizes. Configurations includemultiplexed or non-multiplexed address and data buses using 8-bit, 16-bit, 32-bit,and 16-byte line-sized transfers.2.2.4 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-chipperipherals48 MHz Internal Reference Clock(IRC48M)The IRC48M provides an internally generated clock source. Clock Recoverycircuitry uses the incoming USB data stream to adjust the internal oscillator andenables the internal oscillator to meet the requirements for USB clock tolerance.System 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.Module Functional CategoriesK22F Sub-Family Reference Manual, Rev. 4, 08/201652 NXP Semiconductors
