BUS STROBE AND WAIT PINS
MOTOROLA
PORT A
4 - 15
Adding wait states to external memory accesses can substantially reduce power require-
ments. Consult the
DSP56002 Technical Data Sheet
(DSP56002/D) for specific power
consumption requirements.
4.6
BUS STROBE AND WAIT PINS
The ability to insert wait states using BS and WT provides a means to connect asynchro-
nous devices to the DSP, allows devices with differing timing requirements to reside in the
same memory space, allows a bus arbiter to provide a fast multiprocessor bus access, and
provides another means of halting the DSP at a known program location with a fast restart.
The timing of the BS and WT pins is illustrated in Figure 4-10. Every external access, BS
is asserted concurrently with the address lines in T0. BS can be used by external wait-
BUS
CONTROL
T0
T1
T2
TW
TW
TW
TW
T3
T0
V
CC
+5 V
16
RD
WR
PS
DS
X/Y
WT
BS
24
V
SS
GROUND
ADDRESS BUS
A0 - A15
DATA BUS
D0 - D23
DSP56000/DSP56001
T3
A0 - A15, D0 - D23, PS, DS, X/Y
WT IS
SAMPLED
WT IS
SAMPLED
WT IS
SAMPLED
EM
SD
0
0
0
DE
MB
MA
7
6
5
4
3
2
1
0
SET EM = 1
OPERATING MODE REGISTER
Figure 4-10 Bus Strobe/Wait Sequence
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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