Microcontroller Memory

I will start with a succinct description of the S08’s memory firm. The S08 includes a 65536-byte byte-addressable memory room. This means you will find 65536 places (bytes) where a certain sort of memory or memory-mapped subsystem controller registers could exist. We’ll discover that on the QG8, 56656 of them are unimplemented (Watch the device data sheet). The memory includes a 16-bit address bus – cables with information which explains which one of the 65536 places is being accessed (read or written). This bus is unidirectional – it carries information just from the CPU into the memory system. The memory comes with an 8-bit data bus – cables which carry values to be stored in or retrieved from the addressed location. This bus is bidirectional as either the CPU or the ad790kn device may be the origin of the information and another data’s destination. The very best notation to use for information on the 16-bit address bus (a place specification) is a four hexadecimal-digit amount (hex).

As soon as we get to assembly language we’ll discover that we precede hex constants using a dollar sign ($). Exterior of assembly language we’ll assume we’re writing addresses in hex and shed the $. Similarly the 8-bit data going to or from memory is best expressed as a two-hex-digit number. We’ll shed the $ on these as well. We’ll frequently find it helpful to state the content of a part of memory, but not only the content of one byte. To get rid of the need to compose a speech with every byte of memory content, then we’ll compose the tiniest address worth of a set of memory locations, and then the collection of data bytes following it. The convention is going to be that as we precede left-to-right or even top-to-bottom of this type of data that each data worth speech is one bigger than its predecessor. As soon as we do both we generally go across the page first, then down, however there are instances we might use a multi-column format at which we go down the columns first. It must always be evident

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