
DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR
Information Manual
External Memory Interface
April 1998
6-2
DRAFT COPY
Lucent Technologies Inc.
6.1 EMI Function
(continued)
Bit 14 of the ioc register (EXTROM) can be used with WEROM to download a full 64K of memory (see
Downloading Code into External Program Memory
). If WEROM and EXTROM are both asserted, address bit 15
(AB15) is held low aliasing the upper 32K of external memory in the lower 32K. The WEROM and EXTROM bits
are used by the hardware development system to download a program to EROM space transparently to the user.
The description of the function of each pin follows:
AB[15:0]: This 16-bit external address bus outputs to external memory. The last valid external address is held on
this bus, except if the JTAG has control of the pins or the pins are 3-stated during reset.
DB[15:0]: The 16-bit bidirectional data bus to external data, external instruction/coefficient memory, or memory-
mapped I/O devices used alone or in any combination.
RWN: Read/Write Not; it is an output from the DSP. It indicates a read if logic one and a write if logic zero. In this
manual, the terms read and write are referenced to the DSP; i.e., it is the DSP doing the reading or writing.
EXM: Selects internal or external instruction/coefficient memory space (see
through
6-5
). This input is
latched into the DSP on the rising edge of RSTB. If EXM is latched in low, internal ROM is selected for a portion of
the instruction/coefficient memory space as defined by the MAP selection. If EXM is latched in high, external
memory called EROM is selected for that same portion of instruction/coefficient space.
Memory Segment Enables: Outputs from the DSP. The four leads (EROM, ERAMHI, IO, and ERAMLO) are
used to select one of the four external memory segments. If an enable is low, the segment associated with that
enable is selected. Addresses corresponding to the segments are shown in
through
6-11
. The leading
edge of each can be delayed one half a CKO period by programming the ioc register. This avoids bus contention
and allows the mix of fast and slow external memory, I/O devices, or both.
DSEL
1
: This output is used to select external I/O devices. It is predecoded from memory address 0x4000 in the IO
external memory segment. By default, it is active if low but can be made active-high by programming the ioc regis-
ter.
CKO: This is the clock-out pin. Based on programming of the ioc register (see
Table 6-13
), CKO is one of the fol-
lowing (the term CKO by itself will refer to the free-running CKO):
1. The frequency of the 2x input clock CKI divided by two (called the free-running CKO) or the frequency of the
1x input clock CKI depending on the clock option of the DSP. Or, for the DSP1627/28/29 only, the frequency
of the internal processor clock.
2. The frequency of the 2x input clock CKI divided by two times one plus the number (w) of wait-states (called
the wait-stated CKO)—f
CKI
/(2(1 + w)); w is encoded in the control register mwait. Or, the frequency of the 1x
input clock CKI divided by one plus the number (w) of wait-states—f
CKI
/(1 + w). It depends on the clock
option of the DSP. For the DSP1627/28/29, the frequency of the internal processor clock selected divided by
one plus the number of wait states.
3. Held high.
4. Held low.
5. CKO = CKI for crystal and small-signal options only. For the DSP1627/28/29, CKO = CKI even if PLL is
selected as the internal clock source.
6. Sequenced wait-stated clock that completes two cycles during a sequenced external memory access.
1.DSEL not available in the DSP1627/28/29.
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...