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5.17.2
I2C Electrical Data/Timing
10
8
4
3
7
12
5
6
14
2
3
13
Stop
Start
Repeated
Start
Stop
SDA
SCL
1
11
9
TMS320DM6446
Digital Media System on-Chip
SPRS283–DECEMBER 2005
5.17.2.1
Inter-Integrated Circuits (I2C) Timing
Table 5-75. Timing Requirements for I2C Timings
(1)
(see
Figure 5-57
)
-594
STANDARD
MODE
MIN
10
NO.
FAST MODE
UNIT
MAX
MIN
2.5
MAX
1
t
c(SCL)
Cycle time, SCL
Setup time, SCL high before SDA low (for a repeated START
condition)
Hold time, SCL low after SDA low (for a START and a repeated
START condition)
Pulse duration, SCL low
Pulse duration, SCL high
Setup time, SDA valid before SCL high
Hold time, SDA valid after SCL low (For I
2
C bus devices)
Pulse duration, SDA high between STOP and START
conditions
Rise time, SDA
Rise time, SCL
Fall time, SDA
Fall time, SCL
Setup time, SCL high before SDA high (for STOP condition)
Pulse duration, spike (must be suppressed)
Capacitive load for each bus line
μs
2
t
su(SCLH-SDAL)
4.7
0.6
μs
3
t
h(SCLL-SDAL)
4
0.6
μs
4
5
6
7
t
w(SCLL)
t
w(SCLH)
t
su(SDAV-SCLH)
t
h(SDA-SCLL)
4.7
1.3
0.6
μs
μs
ns
μs
4
250
0
(3)
100
(2)
0
(3)
0.9
(4)
8
t
w(SDAH)
4.7
1.3
μs
9
10
11
12
13
14
15
t
r(SDA)
t
r(SCL)
t
f(SDA)
t
f(SCL)
t
su(SCLH-SDAH)
t
w(SP)
C
b(5)
The I2C pins SDA and SCL do not feature fail-safe I/O buffers. These pins could potentially draw current when the device is powered
down.
A Fast-mode I
2
C-bus device can be used in a Standard-mode I
2
C-bus system, but the requirement t
≥
250 ns must then
be met. This will automatically be the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch
the LOW period of the SCL signal, it must output the next data bit to the SDA line t
max + t
su(SDA-SCLH)
= 1000 + 250 = 1250 ns
(according to the Standard-mode I
2
C-Bus Specification) before the SCL line is released.
A device must internally provide a hold time of at least 300 ns for the SDA signal (referred to the V
IHmin
of the SCL signal) to bridge the
undefined region of the falling edge of SCL.
The maximum t
has only to be met if the device does not stretch the low period [t
] of the SCL signal.
C
b
= total capacitance of one bus line in pF. If mixed with HS-mode devices, faster fall-times are allowed.
1000
1000
300
300
20 + 0.1C
b(5)
20 + 0.1C
b(5)
20 + 0.1C
b(5)
20 + 0.1C
b(5)
300
300
300
300
ns
ns
ns
ns
μs
ns
pF
4
0.6
0
50
400
400
(1)
(2)
(3)
(4)
(5)
Figure 5-57. I2C Receive Timings
Peripheral and Electrical Specifications
187