Texas Instruments TMS320C67X/C67X+ DSP manual 1 -Bit/64-Bit Register Pairs, Register Files Devices

General-Purpose Register Files

Table 2−1. 40-Bit/64-Bit Register Pairs

Register Files
A	B	Devices
A1:A0	B1:B0	C67x DSP
A3:A2	B3:B2
A5:A4	B5:B4
A7:A6	B7:B6
A9:A8	B9:B8
A11:A10	B11:B10
A13:A12	B13:B12
A15:A14	B15:B14
A17:A16	B17:B16	C67x+ DSP only
A19:A18	B19:B18
A21:A20	B21:B20
A23:A22	B23:B22
A25:A24	B25:B24
A27:A26	B27:B26
A29:A28	B29:B28
A31:A30	B31:B30

Figure 2−2. Storage Scheme for 40-Bit Data in a Register Pair

31	Odd register	8 7	0		31	Even register	0
	Ignored
				Read from registers
		39	32		31		0
						40-bit data
					Write to registers
	Odd register	39		32	31	Even register	0
	Zero-filled					40-bit data

2-4 CPU Data Paths and Control SPRU733