
2-32
DSP56007/D MOTOROLA
Specifications
Serial Host Interface (SHI) I
2
C Protocol Timing
Example:
for C
L
= 50 pF, R
P
= 2 k
Ω
, f = 88 MHz, Bypassed Filter mode: The master,
when operating with a DSP56007 SHI I
2
C slave with an 88 MHz operating frequency,
must generate a bus free time greater than 36 ns (T172 slave). Thus, the minimum
permissible t
I
2
CCP
is 56
×
T
C
which gives a bus free time of at least 41 ns (T172 master).
This implies a maximum I
2
C serial frequency of 1010 kHz.
In general, bus performance may be calculated from the C
L
and R
P
of the bus, the
Input Filter modes and operating frequencies of the master and the slave. Table 2-15
contains the expressions required to calculate all relevant performance timing for a
given C
L
and R
P
.
Table 2-15
SHI Improved I
2
C Protocol Timing
Improved I
2
C (C
L
= 50 pF, R
P
= 2 k
Ω
)
No.
Char.
Sym.
Mode
Filter
Mode
Expression
50 MHz
2
66 MHz
3
88 MHz
4
U
n
i
t
Min Max Min Max Min Max
— Tolerable Spike
Width on SCL or
SDA
bypassed
narrow
wide
0
20
100
—
—
—
0
20
100
—
—
—
0
20
100
—
—
—
0
20
100
ns
ns
ns
171 SCL Serial Clock
Cycle
t
SCL
master
slave
bypassed
narrow
wide
bypassed
narrow
wide
t
I
2
CCP
+ 3
×
T
C
+
72 + t
r
t
I
2
CCP
+ 3
×
T
C
+
245 + t
r
t
I
2
CCP
+ 3
×
T
C
+
535 + t
r
4
×
T
C
+ T
H
+
172 + t
r
4
×
T
C
+ T
H
+
366 + t
r
4
×
T
C
+ T
H
+
648 + t
r
1050
1263
1593
500
694
976
—
—
—
—
—
—
1007
1225
1591
478
672
954
—
—
—
—
—
—
981
1199
1557
461
655
937
—
—
—
—
—
—
ns
ns
ns
ns
ns
ns
172 Bus Free Time
t
BUF
master
slave
bypassed
narrow
wide
bypassed
narrow
wide
0.5
×
t
I
2
CCP
–
42 – t
r
0.5
×
t
I
2
CCP
–
42 – t
r
0.5
×
t
I
2
CCP
–
42 – t
r
2
×
T
C
+ 11
2
×
T
C
+ 35
2
×
T
C
+ 70
60
80
100
51
75
110
—
—
—
—
—
—
46
68
102
41
65
100
—
—
—
—
—
—
38.2
60.9
95
33.7
57.7
92.7
—
—
—
—
—
—
ns
ns
ns
ns
ns
ns
173 Start Condition
Set-up Time
t
SU;STA
slave
bypassed
narrow
wide
12
50
150
12
50
150
—
—
—
12
50
150
—
—
—
12
50
150
—
—
—
ns
ns
ns
F
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e
sc
a
le
S
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m
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to
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I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
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Summary of Contents for NXP SYMPHONY DSP56007
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