
Information Manual
DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR
April 1998
External Memory Interface
Lucent Technologies Inc.
DRAFT COPY
6-23
6.4 Timing Examples
(continued)
6.4.7 Read, Read with Delayed Enable
illustrates two back-to-back read cycles and use of delaying the leading edge of one of the enables to
prevent the two external memories from both driving the data bus. The first read cycle is as before with a wait-state
of one, reading the EROM. Two CKO periods after the beginning, the read cycle ends with EROM going high and
the ERAMLO address placed on the address bus. If ERAMLO were to immediately go low selecting the external
data memory and the instruction/coefficient memory had not yet released the bus, a problem could be caused by
both driving the bus. At the least, high currents would result. To avoid this condition, a bit is programmed in the ioc
register to delay the leading edge of ERAMLO by one half a CKO period (see
). During this period, the instruction/coefficient memory 3-states the data bus; and after ERAMLO goes
low, the data memory can start to drive the data bus. The termination of ERAMLO is not delayed because
ERAMLO goes high at the end of the read cycle.
5-4168
Figure 6-9. Read, Read, with Delayed Enable
Sample Instructions:
mwait=0x1002
/*
EROM W=1, ERAMLO W=2
*/
y=a1
x=*pt++
/*
One-cycle read with W=1, pt points to EROM*/
p=x*y
y=*r0++
/*
Two-cycle read with W=2, r0 points to ERAMLO*/
CKO
AB
DB
EROM DATA
RWN
ERAMLO ADDRESS
ERAMLO DATA
EROM
READ CYCLE W = 1
READ CYCLE W = 2
DELAYED EDGE
ERAMLO
EROM ADDRESS
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...