;****************************************************************************************
; file = ex0.asm
; Quick examples of Assembler directives & 28F335 DSP code
; Dr. Eric Schwartz, Feb 20, 2012
; Dr. Eric Schwartz, Feb 12, 2012
; Dr. Eric Schwartz, Jan 23, 2012
; Dr. Eric Schwartz, Jan 24, 2011
; Dr. Karl Gugel, May/2009
;
; To be assembled using Code Composer Studio which requires a linker command
;   file to tell CCR where to place code & data into DSP SRAM.
;   The command linker file used = KG_RAM_Link1.cmd
; Important Code locations are all set up in the command linker file.
;    The code section (signified by a .text assembler directive) starts at 0x9000.
;      .text	RAML1  (internal DSP memory) starting address = 0x9000, 4k Words
;    The data section (signified by a .data assembler directive) starts at 0xA000.
;      .data  RAML2	(internal DSP memory) starting address = 0xA000, 4k Words
;    The bss section is for variables (signified by the first .bss assembler directive)
;      starts at 0xb000
;
; Special Note:
;		Assembler directives are used to place data and variables into memory.
;		They are not F335 instructions and thus are not executed at "run-time".
;		When this program is loaded into memory, the data (created above by the
;		assembler) is also copied down into memory. This is called "load-time".
;
	.global	_c_int00	;This assembler directive allows _c_int00 to be a
					;  global variable. This tells the linker where your
					;  program (.text code) begins and where to boot from.
;
; Additional References:
; 	Assembler Directives: spru513d.pdf
;	Memory Map/Hardware Related: sprs439i.pdf
;	CPU Registers & Assembly Code: spru430e.pdf
;****************************************************************************************

;***************************** Program Constants ****************************************
; Creating constants using the .set assembler directive. This should be at the top of your
; program.  This is like a define statement in C.
num1		.set	0h		;assembly-time constant (hex number)
num2		.set	11110000b	;assembly-time constant (binary no.)
num3		.set	65535		;assembly-time constant (decimal no.)
count		.set	3			;number of characters to add in EEL4744 ('E'+'E'+'L')
data_sect	.set	0xA000		;this is NOT independent of command linker file
bss_sect	.set	0xB000		;this is NOT independent of command linker file
;****************************************************************************************

;******************* DATA ALLOCATION SECTION - Variables/Data ***************************
; Data can go before or after your program code but should not be placed in the middle
; nof a program for clarity reasons.
	.data	;data section, see the command linker file, this puts the
			;  following data defined below in a block of internal SRAM
			;  starting at 0xA000.

counter	.word   0h  	;define word, two bytes placed in memory stating in the data section
num4   	.word   01234h, 0xABCD, 0xFEDC
						;define words (two byte constants) placed in memory
char  	.byte   'E' 	;define string, ASCII characters placed in memory as WORDS!
		.byte   'E', 'L', '4', '7', '4', '4'
		.byte	"0123"	;here is another way to specify a string of WORDS!
		.word	0xfab4	;another way to specify a hex number (WORD)
val1  	.word	32		;places 32 decimal (20 hex) in memory (WORD) at label val1 at load-time
val2  	.word	512		;places 512 decimal(200 hex) in memory (WORD) at label val2 at load-time
val3  	.long	0x12345678	;places two words in memory (lower word/lower addr, LITTLE endian)

;.BSS SECTION is used to reserve space in SRAM for run-time results.
; See the command linker file, the starting address is 0xB000
	.bss	results,3	;reserves three words at label 'results' in the .bss section
	.bss	sum,1		;reserves one word at label 'sum' in the .bss section

;.global directive lets you to see the assigned addresses in map file.
	.global		num1,num2,num3,num3,num4,counter,char,val1,val2,val3,results,sum
;****************************************************************************************

;******************** Brief Introduction to CPU Model ***********************************
; CPU Registers:
;	ACC		Accumulator (32 bits) comprised of AH (upper 16 bits) and AL (lower 16 bits)
;	XAR0	Auxiliary Register0 (32 bits) comprised of AR0H (upper 16 bits) and AR0 (lower 16 bits)
;	XAR1	Auxiliary Register1 (32 bits) comprised of AR1H (upper 16 bits) and AR1 (lower 16 bits)
;	XAR2	Auxiliary Register2 (32 bits) comprised of AR2H (upper 16 bits) and AR2 (lower 16 bits)
;	XAR3	Auxiliary Register3 (32 bits) comprised of AR3H (upper 16 bits) and AR3 (lower 16 bits)
;	XAR4	Auxiliary Register4 (32 bits) comprised of AR4H (upper 16 bits) and AR4 (lower 16 bits)
;	XAR5	Auxiliary Register5 (32 bits) comprised of AR5H (upper 16 bits) and AR5 (lower 16 bits)
;	XAR6	Auxiliary Register6 (32 bits) comprised of AR6H (upper 16 bits) and AR6 (lower 16 bits)
;	XAR7	Auxiliary Register7 (32 bits) comprised of AR7H (upper 16 bits) and AR6 (lower 16 bits)
;	XT	Multiplicand Register (32 bits) comprised of T (upper 16 bits) and TL (lower 16 bits)
;	P	Product Register (32 bits) comprised PH (upper 16 bits) and PL (lower 16 bits)
;	PC	Program Counter (22 bits)
;	SP	Stack Pointer (16 bits)
;	DP	Data Page Register (16 bits)
;	ST1,ST0	Status Registers (flags)

;****************************************************************************************

;****************** F335 Program Examples ***********************
	.text	;Program section, see the command linker file, program code
		;  should be placed in the text section which starts at 0x9000

_c_int00:	;This label tells the linker where the entry (starting) point for
		;  the first instruction in your program.

; Below demonstrates immediate and register to register addressing
; Short example1 to sum 1st three chars in string EEL4744.
; This illustrates immediate, indirect and register addr modes
		MOV	AR0,#char   	;address of 1st char in EEL4744
		MOV	AR1,#sum   		;address of where final sum (result)will be stored
		MOV	AR2,#counter	;address of counter saved in memory
		MOV	AH,#count   	;load the count value & save in memory counter
		MOV	*AR2,AH
		MOV	AL,#0   		;clear initial sum
TOP1		ADD	AL,*AR0   	;add char value to sum
		INC	AR0     		;increment pointer used to get a char value
		DEC	*AR2    		;decrement counter in memory
		B	TOP1,NEQ		;if the Z flag is 0, branch up and repeat adding
		MOV	*AR1,AL
		NOP				;No operation to view sum in memory at addr results
		NOP				;  put some instructions (space) inbetween the next example
						;  for stepping through with the debugger so no regs change.

; Short example2 to illustrate direct addressing and mathematical & shift operations.
		MOV	DP,#data_sect>>6	;set datapage pointer to point to .data section
		MOV	T,@val1				;load T using direct addressing mode
		MPYU	ACC,T,@val2		;val1[] * val2[] => ACC, 16 bit unsigned multiply

		MOV	DP,#bss_sect>>6		;set datapage pointer to point to .bss section
		MOV	@results,AL			;save lower word only, which assumes answers is 16 bits or less

		MOV	DP,#data_sect>>6	;set datapage pointer back to .data section
		MOV	AL,@val1			;add val1[] + val2[]
		ADD	AL,@val2
		MOV	DP,#bss_sect>>6		;set datapage pointer to point to .bss section
		MOV	@results+1,AL		;save val1[] + val2[]

;Shift left example
		MOV	AH,#num3		;set AH to a predetermined value to see if the
							;  next instruction affects AH
		LSL	AL,#5			;logical shift left AL by 5 places
		MOV	@results+2,AL

		NOP
		NOP
END1	B	END1,UNC		;infinite loop to prevent program from trying to execute
							;  un-initialized (no program) memory.