DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR
Information Manual
Core Architecture
April 1998
5-14
DRAFT COPY
Lucent Technologies Inc.
5.3 Y Address Arithmetic Unit (YAAU)
(continued)
5.3.2 Y-Memory Space
The 64K memory space is divided into four segments: RAM, ERAMLO, ERAMHI, and IO as shown in
. The selection of a segment is automatic depending on the Y address in the YAAU. Unlike the X-memory
space, there is only one memory map for the four segments. The segment for the internal RAM is further divided
into multiple 1K banks. The addresses are decoded in the YAAU and an enable is provided for each of the external
segments and each of the RAM banks.
5.3.3 Register Descriptions
Registers r0—r3 provide register-indirect addressing. They are 16-bit unsigned registers that contain addresses
pointing to RAM locations for reading or writing. Pointers r0—r3 can be automatically postmodified by 0, +1, –1,
+2, the contents of the j register, or the contents of the k register. The j and k registers contain 16-bit, two's com-
plement signed numbers with a range of –32,768 to +32,767. The k register and the +2 increment are only used by
the compound addressing instructions. The adder in the YAAU postmodifies the contents of the r0—r3 registers.
The registers, except for ybase, in the YAAU are the only ones that can be loaded with the short immediate instruc-
tion SR = IM9. Nine bits of data from the instruction are loaded into the lowest 9 bits of one of the YAAU registers
as specified in the instruction. The upper 7 bits are filled with zeros except for the j and k registers that are sign-
extended.
The ybase register provides direct addressing of data memory (see
). The upper 11 bits
of the address are held in the upper portion of the ybase register (labelled BASE in
). If a
data move instruction using direct data addressing is executed, the instruction contains 4 bits selecting one of 16
registers (e.g., r0 or a0) as the source or destination for the data move and 5 bits that form the offset part of the
address (see
Section 4.3.2, Compound Addressing
Section 4.5.3, Data Move Instructions
). The five offset bits
are concatenated to the 11 base bits to form an address. The corresponding location becomes a source or desti-
nation for the data move.
5.3.4 Addressing Modes
Four modes of addressing are supported by the YAAU (see also
):
1. Register-indirect: The most frequently used mode in which one of the r0—r3 registers contains an address that
points to a location in data memory. The address can be postmodified (see
Section 5.3.3, Register Descrip-
).
2. Direct data addressing: The lower 5 bits in the direct data instruction (see
Section 4.5.3, Data Move Instruc-
) are concatenated with the upper 11 bits previously stored in the ybase register to form the address.
3. Compound addressing: Data contained in a memory location pointed to by one of the r0—r3 registers is
swapped with the contents of a register specified directly in the compound addressing instruction (see
). Four choices of postmodification are available (see
).
4. Virtual-shift (modulo) addressing: A special case of register-indirect addressing in which an implicit circular
shift register is established for zero-overhead virtual-shift addressing. This mode enables the creation of an arbi-
trarily-sized portion of contiguous RAM locations to behave as if it were a physical delay or shift register without
actually moving data within RAM. The virtual-shift buffer is implemented in memory by storing the data at fixed
locations and incrementing the memory pointer in a modular fashion. The YAAU registers rb and re contain
addresses that establish the lower and upper boundaries of the virtual-shift buffer. Virtual-shift addressing is nor-
mally disabled and is enabled by writing a nonzero value to re. re is cleared on reset.
The following sections describe direct data addressing and virtual-shift addressing in further detail.
Содержание DSP1611
Страница 18: ...Chapter 1 Introduction...
Страница 27: ...Chapter 2 Hardware Architecture...
Страница 52: ...Chapter 3 Software Architecture...
Страница 116: ...Chapter 4 Instruction Set...
Страница 154: ...Chapter 5 Core Architecture...
Страница 176: ...Chapter 6 External Memory Interface...
Страница 208: ...Chapter 7 Serial I O...
Страница 237: ...Chapter 8 Parallel I O DSP1617 Only...
Страница 261: ...Chapter 9 Parallel Host Interface PHIF DSP1611 18 27 28 29 Only...
Страница 275: ...Chapter 10 Bit I O Unit...
Страница 284: ...Chapter 11 JTAG Test Access Port...
Страница 306: ...Chapter 12 Timer...
Страница 313: ...Chapter 13 Bit Manipulation Unit...
Страница 325: ...Chapter 14 Error Correction Coprocessor DSP1618 28 Only...
Страница 350: ...Chapter 15 Interface Guide...
Страница 367: ...Appendix A Instruction Encoding...
Страница 379: ...Appendix B Instruction Set Summary...
Страница 381: ...aD extractz aS IM16 B 52 aD insert aS arM B 53 aD insert aS IM16 B 54 aD aS aaT B 55...
Страница 437: ...Index...