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DSP96002 USER’S MANUAL
MOTOROLA
5.16.3.5 Case 5 – Bus Lock during RMW
If the device requesting mastership asserts
—
B
–
R and the arbiter asserts the requesting devices’
—
B
–
G
and
—
B
–
B is deasserted, then the requesting device will assert
—
B
–
A. If a read-modify-write (RMW) in-
struction which accesses external memory is being executed, and the bus arbiter deasserts
—
B
–
G, then
—
B
–
A will remain asserted until the entire RMW instruction completes execution.
—
B
–
A will then be deas-
serted thereby relinquishing the bus. Note that during external RMW instruction execution,
—
B
–
L is assert-
ed. In general, the
—
B
–
L signal can be used to ensure that a multiport memory can only be written by one
master at a time. That is, referring to Figure 2-10,
—
B
–
L can be input from DSP #1to the memory controller
which prevents
—
T
–
A from being asserted by the controller (thereby suspending the memory access by
DSP #2) until DSP #1 completes its RMW access.
5.16.3.6 Case 6 – Bus Park
The device requesting mastership asserts
—
B
–
R; the arbiter asserts the requesting devices’
—
B
–
G and
—
B
–
B is deasserted indicating the bus is not busy – the requesting device will assert
—
B
–
A. When the
requesting device no longer requires the bus it will deassert
—
B
–
R; if the bus arbiter leaves
—
B
–
G assert-
ed because other requests are not pending, then
—
B
–
A will remain asserted. This condition is called bus
parking and eliminates the need for the last bus master to rearbitrate for the bus during its next external
access.
Dual Port
Memory
Controller
DSP96002
#2
#1
RMW
—
B
–
L
—
T
–
A
Figure 2-10. Bus Lock During RMW
DSP96002
Summary of Contents for DSP96002
Page 3: ...1 2 DSP96002 USER S MANUAL MOTOROLA ...
Page 38: ...MOTOROLA DSP96002 USER S MANUAL 3 15 Figure 3 4 Modulo Arithmetic Unit Block Diagram ...
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Page 76: ...MOTOROLA DSP96002 USER S MANUAL 5 23 Figure 5 8 Address Modifier Summary ...
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Page 101: ...MOTOROLA DSP96002 USER S MANUAL 7 15 Figure 7 9 HI Block Diagram One Port ...
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Page 181: ...MOTOROLA DSP96002 USER S MANUAL 10 15 Figure 10 8 Program Address Bus FIFO ...
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Page 460: ...A 272 DSP96002 USER S MANUAL MOTOROLA SIOP Not affected ...
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Page 718: ...MOTOROLA DSP96002 USER S MANUAL B 199 ...
Page 871: ... MOTOROLA INC 1994 MOTOROLA TECHNICAL DATA SEMICONDUCTOR M Addendum ...
Page 888: ...MOTOROLA INDEX 1 INDEX ...
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