BASICS OF MSP430 & INTERFACING MICRO-SD CARD WITH IT.

BASICS OF MSP430 MICROCONTROLLER INTRODUCTION TO MSP430 :- The MSP430 is a mixed signal processor family from Texas Instuments. Built around a 16-bit CPU, the MSP430 is designed for low cost and, specifically, low power consumption embedded applications. The MSP430 can be used for low powered embedded devices. The electric current drawn in idle mode can be less than 1 µA. The top CPU speed is 25 MHz. It can be throttled back for lower power consumption. The MSP430 also uses six different low-power modes, which can disable unneeded clocks and CPU. Additionally, the MSP430 is capable of wake-up times below 1 microsecond, allowing the microcontroller to stay in sleep mode longer, minimizing its average current consumption.

MORE ON CLOCK SYSTEMS IN MSP430 The UCS module includes up to five clock sources:- XT1CLK:-Generally 32KHz but may be extended VLOCLK:-10KHz REFOCLK:-32KHz DCOCLK:-internal DCO XT2CLK:-from 4 MHz to 32 MHz Conflicting requirements typically exist in battery-powered applications: Low clock frequency for energy conservation and time keeping High clock frequency for fast response times and fast burst processing capabilities Clock stability over operating temperature and supply voltage Low-cost applications with less-constrained clock accuracy requirements Three clock signals are available from the UCS module:- ACLK(32KHz),SMCLK(2MHz):-The ACLK is software selectable as XT1CLK, REFOCLK, VLOCLK,DCOCLK,DCOCLKDIV, and when available, XT2CLK.This are used by peripheral devices. MCLK(1MHz):-Same as above but this is used by CPU.

BASICS THAT WE WORKED ON FOR LAST WEEK:- Timers:-The 16-bit timer/counter register, TAxR(say), increments or decrements (depending on mode of operation) with each rising edge of the clock signal. TAxR can be read or written with software. Additionally, the timer can generate an interrupt when it overflows. Modes of operation :- Up Mode(counting upto TAXCCR0 value,on overflow generates interrupts) Up/Down Mode(same as up mode but also conts in reverse way) Continuous mode(counting upto FFFFh value,on overflow generates interrupts)

BASICS THAT WE WORKED ON FOR LAST WEEK:- RTC(Real Time Clock):-A real time clock can be powered by a Li-ion battery & can function even when the system is under standby -condition Calendar Mode:-A 32-bit register with 4 separate registers of 8-bit,each for secs,mins,hour & day of week.In RTCA of MSP430 there is also a facility for alarm.User enters the time & day for alarm to generate interuppt. Counter Mode:-This works exactly the same way as a 32 bit timer module.

BASICS THAT WE WORKED ON FOR LAST WEEK:- USCI [UART(Universal Asynchronous receival & transmission)]:- In UART mode, the USCI transmits and receives characters at a bit rate asynchronous to another device. Timing for each character is based on the selected baud rate of the USCI. The transmit and receive functions use the same baud-rate frequency.

INTERFACING MICRO-SD CARD WITH MSP430 As you all know why micro-sd card is used for,I would like to discuss more on Micro-sd interfacing. Well to put in raw data & fetching is as good as serial communication,However for a computer to input or see a Text File,a Doc File It interacts with micro-sd with certain protocols. In the same way for a controller to input a text file(say),it requires a set of standard file systems eg:-FAT,NTFS.

MORE ON FAT A volume's data area is divided up into identically sized clusters, small blocks of contiguous space. Cluster sizes vary depending on the type of FAT file system being used and the size of the partition; typically cluster sizes lie somewhere between 2 KB and 32 KB. Each file may occupy one or more of these clusters depending on its size; thus, a file is represented by a chain of these clusters (referred to as a singly linked list). However these clusters are not necessarily stored adjacent to one another on the disk's surface but are often instead fragmented throughout the Data Region. The File Allocation Table (FAT) is contiguous number of sectors immediately following the area of reserved sectors. It represents a list of entries that map to each cluster on the volume. Each entry records one of five things:- the cluster number of the next cluster in a chain a special end of cluster-chain (EOC) entry that indicates the end of a chain a special entry to mark a bad cluster a zero to note that the cluster is unused(deleted files) Each version of the FAT file system uses a different size for FAT entries. Smaller numbers result in a smaller FAT, but waste space in large partitions by needing to allocate in large clusters. The FAT12 file system uses 12 bits per FAT entry.

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