HD6417615 Hitachi Semiconductor, HD6417615 Datasheet - Page 77

• Manufacturer Part Number: HD6417615
• Description: Hardware Manual
• Manufacturer: Hitachi Semiconductor

Modulo Addressing: The chip has a modulo addressing mode, just as other DSPs do. Address
registers are updated in the same manner as with other modes. When the address pointer value
becomes the same as a previously established modulo end address, the address pointer becomes
the modulo start address.
Modulo addressing is valid only with X, Y data transfer instructions (MOVX.W, MOVY.W).
When the DMX bit of the SR register is set, the X address register enters modulo addressing
mode; when the DMY bit of the SR register is set, the Y address register does so. Modulo
addressing is valid only for either the X or the Y address register; it is not possible to make them
both modulo addressing mode at the same time. Therefore, do not simultaneously set the DMX
and DMY. If they happen to be set at the same time, only the DMY side is valid.
The MOD register is used to designate the start and end addresses of the modulo address area; it
stores the MS (modulo start) and ME (modulo end). An example of MOD register (MS, ME)
usage is indicated below.
Designate the start and end addresses in MS and ME, and then set the DMX or DMY bit to 1. The
contents of the address register are compared with ME. If they match ME, the start address MS is
stored in the address register. The lower 16 bits of the address register are compared with ME. The
maximum modulo size is 64 kbytes. This is sufficient for X, Y data memory accesses. Figure 2.11
shows a block diagram of modulo addressing.
ModAddr:
ModStart: .DATA
ModEnd:
MOV.L ModAddr,Rn;
LDC Rn,MOD;
.DATA.W
.DATA.W
.DATA
:
mEnd;
mStart;
ModEnd
Rn=ModEnd, ModStart
ME=ModEnd, MS=ModStart
ModStart
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