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Microcontroller devices with integrated I/O and memory on-chip sometimes had no, or a small, address bus available for external devices. For example, a microcontroller family available with a 2 kilobyte address space might have a variant that brought out an 11 line address bus for an external ROM; this could be done by reassigning I/O pins as address bus pins.
Special function registers are in the upper area of addressable memory, from address 0x80 to 0xFF. This area of memory cannot be used for data or program storage, but is instead a series of memory-mapped ports and registers. All port input and output can therefore be performed by memory move operations on specified addresses in the SFR region.
The H08A has a smaller 14-bit ROM space and 11-bit RAM space (vs. up to 20 and 12 bits on the PIC18), but it is not clear if this is an architectural limit or just that of current products. The H08A is missing the PIC18 PUSH , [ 30 ] DAW , TBLWR , CALLW , RESET , MOVF , SUBFWB , and NEGF instructions.
Writes to low-order bytes are buffered until the highest-order byte is written, upon which the entire multi-byte register is updated atomically. Later XMEGA cores (specifically, the B, C, and AU models such as the ATxmega16A4U, but not the earlier A, D and E models such as the ATxmega16D4) add four atomic read-modify-write instructions ...
The ATmega series features microcontrollers that provide an extended instruction set (multiply instructions and instructions for handling larger program memories), an extensive peripheral set, a solid amount of program memory, as well as a wide range of pins available.
MCS-51-based microcontrollers typically include one or two UARTs, two or three timers, 128 or 256 bytes of internal data RAM (16 bytes of which are bit-addressable), up to 128 bytes of I/O, 512 bytes to 64 KB of internal program memory, and sometimes a quantity of extended data RAM (ERAM) located in the external data space. External RAM and ROM ...
Automotive Microcontrollers The RL78 F12 , F13 , F14 , & F15 devices replaced the original NEC 78K0R/Fx3 devices with many updates including die shrink, faster core speed (32MHz), improved on-chip debug capability, new peripherals, safety features, and expanded package and memory options.
Memory hierarchy of an AMD Bulldozer server. The number of levels in the memory hierarchy and the performance at each level has increased over time. The type of memory or storage components also change historically. [6] For example, the memory hierarchy of an Intel Haswell Mobile [7] processor circa 2013 is: