The Microcontroller Idea book (Jan Akelson, 1997)

Programs for Loading Files

Listing B-2 (page 4 of 4).

rem Error messages and program termination

3000 PRINT CR ,"Line “,LINE,” EXPECTED ’:’, FOUND ’",CHR(C),"’" : END

3010 PRINT CR, “Line ”, LINE, “: Unknown record type”, CH : END

3020 PRINT CR, “Line ”, LINE, “: Checksum failure. Expected”,

3025 PH0. ABS (CHECK - CH) : END rem Normal program exit point

3030 PRINT CR, “Received an End record in line”,LINE : END 3040 PRINT CR, “Line”, LINE, “: Illegal EPROM/EEPROM ad-

dress :”,

3050 PH0. ADDR : END

3060 PRINT CR, “Line”, LINE, “: PGM error at address”, 3070 ADDR = DBY (1AH) * 256 + DBY (18h) : PH0. ADDR 3080 PH0. “The byte at”, address, “ is”, XBY(ADDRESS) 3090 PH0. “The byte should be”,DBY (28) : END

3100 PH0. CR, “Line”, LINE, “: Error writing at address”, ADDR

3110 PH0. “The byte at”, addr, “ is”, XBY(ADDR) 3120 PH0. “The byte should be”, XBY (I) : END REM verify CBY() read in RAM failed:

3130 PH0. “The byte at”,addr," failed a verify with CBY" : END

Number Systems

Appendix C

Number Systems

Designing and programming microcontroller circuits often involves working with different number systems, including hexadecimal and binary as well as familiar decimal numbers. Hexadecimal and binary systems are useful because they offer an easy-to-interpret way of expressing the bitand byte-oriented values that computers use. This appendix is a review of these number systems.

About Number Systems

A number system provides a way to express numerical information. Each of the number systems described below varies in the number, or quantity, on which it is based (10, 2, or 16). This determines, among other things, how many characters you need to express a given quantity.

Decimal Numbers

In the decimal number system used in everyday (non-computer) life, there are ten digits (0-9). Each digit in a number represents a value raised to a power of 10.

Appendix C

This table shows the value of each digit in the decimal number 193:

Binary Numbers

In the binary number system, each digit represents a value raised to a power of 2. The numbers use only two of the ten decimal digits (0 and 1).

Binary representations are useful when you need to quickly see the value of each bit in a byte. For example, you might want to set, clear, toggle, or read a bit in one of the 8052’s special function registers (TCON, PCON, and so on). Or, in a control circuit, individual bits might control switches or relays. BASIC-52’s logical operators offer a way to control and display individual bit values.

This table shows the value of each digit in 1100 0001, which is the binary representation of the decimal number 193:

Hexadecimal Numbers

In the hexadecimal (or hex) number system, each character represents a value raised to a power of 16. There are 16 characters, with the letters A through F representing the decimal values 10 through 15.

Because each character in a hex number represents 4 bits, hex numbers are a convenient, compact way to express 8-bit or 16-bit numbers. In BASIC-52, you enter hex values at the host system’s keyboard by adding a trailing h to the number. (Example: 1Fh.) If the first character is in the range A-F, you must also add a leading 0. (Example: 0E9h.) BASIC-52’s PH0. and PH1. operators display numbers in hex format on the host computer’s screen.

Number Systems

This table shows the value of each character in C1h, which is the hexadecimal representation of the decimal number 193:

Binary-coded Decimal Numbers

Binary-coded decimal, or BCD, is yet another way of expressing numbers. It allows easy translation of binary bits to decimal values. Chapter 10 has more on this number system.

Kilobytes and Megabytes

Two other popular terms for dealing with quantities in the computer world are kilobyte and

Megabyte.

In the metric system of measurement, kilo means 1000, but in the computer world, it commonly refers to 1024 (210, or 400h in hexadecimal). So, an 8-kilobyte RAM chip actually stores 8192 bytes, not 8000. “K” is short for kilobyte: 8K equals 8 kilobytes.

In an similar way, in the metric system, Mega means a million, but in the computer world, it commonly refers to 1,048,576 (220, or 1000h in hexadecimal). One Megabyte equals 1024 kilobytes. “M” is short for Megabyte: 8M equals 8 Megabytes.

Index

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Index

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Index

S V

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