MCU Keywords Registers and Operators-EEWORLD

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Appendix 1 Keywords in C51

Keywords	use	illustrate
auto	Storage Type Description	Used to describe local variables. The default value is
break	Program Statements	Exit the innermost loop
case	Program Statements	Selections in a Switch Statement
char	Data Type Description	Single-byte integer or character data
const	Storage Type Description	A constant value that cannot be changed during program execution
continue	Program Statements	Turn to the next cycle
default	Program Statements	Failed Selection in Switch Statement
do	Program Statements	Constructing a do..while loop structure
double	Data Type Description	Double-precision floating point numbers
else	Program Statements	Constructing if..else selection structure
enum	Data Type Description	enumerate
extern	Storage Type Description	Global variables declared in other program modules
flost	Data Type Description	Single-precision floating point numbers
for	Program Statements	Constructing a for loop structure
goto	Program Statements	Constructing a goto transfer structure
if	Program Statements	Constructing if..else selection structure
int	Data Type Description	Basic integers
long	Data Type Description	Long integer
register	Storage Type Description	Using variables stored inside the CPU
return	Program Statements	Function Returns
short	Data Type Description	Short integer
signed	Data Type Description	Signed number, the highest bit of binary data is the sign bit
sizeof	Operators	Counts the number of bytes of an expression or data type
static	Storage Type Description	Static variables
struct	Data Type Description	Structure type data
swicth	Program Statements	Constructing a switch selection structure
typedef	Data Type Description	Redefine data types
union	Data Type Description	Union type data
unsigned	Data Type Description	Unsigned data
void	Data Type Description	Untyped data
volatile	Data Type Description	This variable can be implicitly changed during program execution
while	Program Statements	Constructing while and do..while loop structures

Appendix 1-1 ANSIC standard keywords

Keywords	use	illustrate
bit	Bit Scalar Declaration	Declare a bit scalar or bit type function
sbit	Bit Scalar Declaration	Declare a bit-addressable variable
Sfr	Special Function Register Declaration	Declare a special function register
Sfr16	Special Function Register Declaration	Declare a 16-bit special function register
data	Memory Type Description	Directly addressable internal data memory
bdata	Memory Type Description	Bit-addressable internal data memory
idata	Memory Type Description	Indirectly addressable internal data memory
pdata	Memory Type Description	Paged addressing of external data memory
xdata	Memory Type Description	External data storage
code	Memory Type Description	Program Memory
interrupt	Interrupt function description	Define an interrupt function
reentrant	Reentrant Function Description	Define a reentrant function
using	Register Group Definition	Define the chip's working registers

Appendix 1-2 Extended keywords of the C51 compiler

Appendix 2 AT89C51 special function register list (applicable to chips with the same architecture)

symbol	address	Notes
*ACC	E0H	accumulator
*B	F0H	Multiplication register
*PSW	D0H	Program status word
SP	81H	Stack Pointer
DPL	82H	Data memory pointer lower 8 bits
DPH	83H	Data memory pointer upper 8 bits
*IE	A8H	Interrupt Enable Controller
*IP	8H	Interrupt Priority Controller
*P0	80H	Port 0
*P1	90H	Port 1
*P2	A0H	Port 2
*P3	B0H	Port 3
PCON	87H	Power control and baud rate selection
*SCON	98H	Serial port controller
SBUF	99H	Serial Data Buffer
*TCON	88H	Timer control
TMOD	89H	Timer mode selection
TL0	8A	Timer 0 lower 8 bits
TL1	8BH	Timer 1 lower 8 bits
TH0	8CH	Timer 0 lower 8 bits
TH1	8DH	Timer 1 high 8 bits

Special function registers marked with * are bit-addressable registers.

Appendix III Operator precedence and associativity

level	category	name	Operators	Combination
1	Cast, array, structure, union	Type conversion	( )	Right Associative
		Subscript	[ ]
		Accessing structure or union members	->or.
2	logic	Logical NOT	!	Left Associative
	Font	Bitwise inversion	~
	Increment	plus one	++
	Reduction	minus one	--
	pointer	Get address	&
	pointer	Get content	*
	arithmetic	Monocular subtraction	-
	Length calculation	Length calculation	sizeof
3	arithmetic	take	*	Right Associative
		remove	/
		Taking the mold	%
4	Arithmetic and pointer operations	add	+
4	Arithmetic and pointer operations	reduce	-
5	Font	Shift Left	<<
5	Font	Shift Right	>>
6	relation	greater or equal to	>=
		more than the	>
		Less than or equal to	<=
		Less than	<
7		Equal to	==
7		not equal to	!=
8	Font	Bitwise AND	&
9		Bitwise XOR	^
10		Bitwise OR	\|
11	logic	Logical AND	&&	Left Associative
12	logic	Logical OR	\|\|
13	condition	Conditional Operations	?:
14	Assignment	Assignment	=
14	Assignment	Compound Assignment	Op=
15	comma	Comma operation	,	Right Associative

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Keil simulation shows "Can not read register xx while CPU is running"

The program can be downloaded using jlink, but the following error always occurs during online simulation: ***JLink Error: Could not start CPU core. (ErrorCode: -1) **JLink Warning: CPU could not be halted ***JLink Error: Can not read register 15 (R15) while CPU is running ***JLink Error: Can not read register 16

[Microcontroller]

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