Analog Devices ADSP-21020 manual Fixed-Point Floating-Point

ADSP-21020

	Table III. Universal Registers
Name	Function
Register File
R15–R0	Register file locations
Program Sequencer
PC*	Program counter; address of instruction cur-
	rently executing
PCSTK	Top of PC stack
PCSTKP	PC stack pointer
FADDR*	Fetch address
DADDR*	Decode address
LADDR	Loop termination address, code; top of loop
	address stack
CURLCNTR	Current loop counter; top of loop count stack
LCNTR	Loop count for next nested counter-controlled
	loop
Data Address Generators
I7–I0	DAG1 index registers
M7–M0	DAG1 modify registers
L7–L0	DAG1 length registers
B7–B0	DAG1 base registers
I15–I8	DAG2 index registers
M15–M8	DAG2 modify registers
L15–L8	DAG2 length registers
B15–B8	DAG2 base registers
Bus Exchange
PX1	PMD-DMD bus exchange 1 (16 bits)
PX2	PMD-DMD bus exchange 2 (32 bits)
PX	48-bit PX1 and PX2 combination
Timer
TPERIOD	Timer period
TCOUNT	Timer counter
Memory Interface
DMWAIT	Wait state and page size control for data
	memory
DMBANK1	Data memory bank 1 upper boundary
DMBANK2	Data memory bank 2 upper boundary
DMBANK3	Data memory bank 3 upper boundary
DMADR*	Copy of last data memory address
PMWAIT	Wait state and page size control for program
	memory
PMBANK1	Program memory bank 1 upper boundary
PMADR*	Copy of last program memory address
System Registers
MODE1	Mode control bits for bit-reverse, alternate reg-
	isters, interrupt nesting and enable, ALU satu-
	ration, floating-point rounding mode and
	boundary
MODE2	Mode control bits for interrupt sensitivity,
	cache disable and freeze, timer enable, and I/O
	flag configuration
IRPTL	Interrupt latch
IMASK	Interrupt mask
IMASKP	Interrupt mask pointer (for nesting)
ASTAT	Arithmetic status flags, bit test, I/O flag values,
	and compare accumulator
STKY	Sticky arithmetic status flags, circular buffer
	overflow flags, stack status flags (not sticky)
USTAT1	User status register l
USTAT2	User status register 2

*read-only

Refer to User’s Manual for bit-level definitions of each register.

Table IV. ALU Compute Operations

Fixed-Point	Floating-Point
Rn = Rx + Ry	Fn = Fx + Fy
Rn = Rx – Ry	Fn = Fx – Fy
Rn = Rx + Ry, Rm = Rx – Ry	Fn = Fx + Fy, Fm = Fx – Fy
Rn = Rx + Ry + CI	Fn = ABS (Fx + Fy)
Rn = Rx – Ry + CI – l	Fn = ABS (Fx – Fy)
Rn = (Rx + Ry)/2	Fn = (Fx + Fy)/2
COMP(Rx, Ry)	COMP(Fx, Fy)
Rn = –Rx	Fn = –Fx
Rn = ABS Rx	Fn = ABS Fx
Rn = PASS Rx	Fn = PASS Fx
Rn = MIN(Rx, Ry)	Fn = MIN(Fx, Fy)
Rn = MAX(Rx, Ry)	Fn = MAX(Fx, Fy)
Rn = CLIP Rx BY Ry	Fn = CLIP Fx BY Fy
Rn = Rx + CI	Fn = RND Fx
Rn = Rx + CI – 1	Fn = SCALB Fx BY Ry
Rn = Rx + l	Rn = MANT Fx
Rn = Rx – l	Rn = LOGB Fx
Rn = Rx AND Ry	Rn = FIX Fx BY Ry
Rn = Rx OR Ry	Rn = FIX Fx
Rn = Rx XOR Ry	Fn = FLOAT Rx BY Ry
Rn = NOT Rx	Fn = FLOAT Rx
	Fn = RECIPS Fx
	Fn = RSQRTS Fx
	Fn = Fx COPYSIGN Fy

Rn, Rx, Ry R15–R0; register file location, fixed-point

Fn, Fx, Fy F15–F0; register file location, floating point

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