HD6417727BP160CV Datasheet, PDF (89/1098 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family/ SH7700 Series

Section 2 CPU
2.1.3 System Registers
The SH7727 has four system registers, MACL, MACH, PR and PC (figure 2.6).
31
MACH
MACL
31
PR
31
PC
0
Multiply and accumulate high and low registers
(MACH/L)
Store the results of multiplicationand accumulation
operations.
0
Procedure register (PR)
Stores the subroutine procedure return address.
0
Program counter (PC)
Indicates the starting address that is four addresses ahead.
Figure 2.6 System Registers
DSR, A0, X0, X1, Y0 and Y1 registers are also treated as system registers. So, data transfer
instructions between general registers and system registers are supported for them.
2.1.4 DSP Registers
The SH7727 has eight data registers and one control register (figure 2.7). The data registers are
32-bit width with the exception of registers A0 and A1. Registers A0 and A1 include 8 guard bits
(fields A0G and A1G), giving them a total width of 40 bits.
Three types of operations access the DSP data registers. First one is the DSP data. When a DSP
fixed-point data operation uses A0 or A1 for source register, it uses the guard bits (bits 39 to 32).
When it uses A0 or A1 for destination register, bits 39 to 32 in the guard bit are valid. When a
DSP fixed-point data operation uses the DSP registers other than A0 and A1 for source register, it
sign-extends the source value to bits 39 to 32. When it uses them for destination register, the bits
39 to 32 of the result is discard.
Second one is X and Y data transfer operation, “MOVX.W MOVY.W”. This operation accesses
the X and Y memories through 16-bit X and Y data buses (figure 2.8). Registers to be loaded or
stored by this operation are always upper 16 bits (bits 31 to 16). X0 and X1 can be destination of
the X memory load and Y0 and Y1 can be destination of Y memory load, but other register cannot
be destination register of this operation.
Rev.6.00 Mar. 27, 2009 Page 31 of 1036
REJ09B0254-0600