Texas Instruments TMS320 DSP manual Ssp

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TMS320C55x Rules and Guidelines

If the algorithm does not use B-bus, then the first column must be zero. If there is more than one block that is accessed by the B-bus, then all the block numbers must be specified in the second column as shown in the above example.

Example 2:

Any static-data that is accessed by the B-bus must be documented as per the Rule 37 as follows:

Data section names that are accessed by the

B-bus

.data

.coefwords

This way, the client will know which of the memory blocks and data-sections must be placed in on-chip memory for the correct execution of the algorithm.

5.5.5 Register Conventions

This section describes the rules and guidelines that apply to the use of the TMS320C55x on-chip registers. Note that an algorithm must not access any register that is not described here.

The table below describes all of the registers that may be accessed by an algorithm. Please refer to TMS320C55x Optimizing C/C++ Compiler User's Guide (SPRU281), Runtime Environment chapter, for more details about the runtime conventions followed by the compiler.

	Register	Use	Type
	(X)AR0, (X)AR1, (X)AR2, (X)AR3, (X)AR4	Function arguments: data pointers (16- or 23-bit) or	Scratch (local)
		data values (16-bit)
	(X)AR5, (X)AR6, (X)AR7	C compiler register variables	Preserve (local)
	AC0, AC1, AC2, AC3	16-bit, 32-bit and 40-bit data or 24-bit code pointers	Scratch (local)
	T0, T1	Function arguments: 16-bit data values	Scratch (local)
	T2, T3	C compiler expression registers	Preserve (local)
	SSP	System Stack Pointer	Preserve (local)
	SP	Stack Pointer	Preserve (local)
	ST0, ST1, ST2, ST3	Status registers	Preserve (local)
	IFR0, IMR0, IFR1, IMR1	Interrupt flag and mask register	Read-only (global)
	TRN0, TRN1	Transition registers	Scratch (local)
	BK03, BK47, BKC	Circular Buffer Offset registers	Scratch (local)
	BRC0, BRC1	Block Repeat Counter registers	Scratch (local)
	RSA0, REA0, RSA1, REA1	Block repeat start and end address registers	Scratch (local)
	CDP	Coefficient Data Pointer	Scratch (local)
	XDP	Extended Data page pointer	Scratch (local)
	DP	Memory data page start address	Scratch (local)
	PDP	Peripheral Data page start address	Scratch (local)
	BOF01, BOF23, BOF45, BOF67, BOFC	Circular buffer offset registers	Scratch (local)
	BIOS	Data page pointer storage	Read-only (global)
	BRS0, BRS1	Block repeat save registers	Scratch (local)
	CSR	Computed Single Repeat	Scratch (local)
	RPTC	Repeat Single Counter	Scratch (local)
	XSP	Extended data Stack pointer	Preserve (local)
	XCDP	Extended coeff page pointer	Scratch (local)
	IVPD	Interrupt vector pointer DSP	Read-only (global)
	IVPH	Interrupt vector pointer host	Read-only (global)
54	DSP-Specific Guidelines	SPRU352G –June 2005 –Revised February 2007
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