TMS320VC5504 datasheet(97/128 Pages) TI

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6.12.2

I2C Electrical Data/Timing

Stop

Start

Repeated

Start

Stop

SDA

SCL

TMS320VC5504

Fixed-Point Digital Signal Processor

www.ti.com

SPRS609A – JUNE 2009 – REVISED JULY 2009

Table 6-21. Timing Requirements for I2C Timings(1) (see Figure 6-22)

CVDD = 1.05 V

CVDD = 1.3 V

NO.

STANDARD

UNIT

FAST MODE

MODE

MIN

MAX

MIN

MAX

tc(SCL)

Cycle time, SCL

2.5

µs

Setup time, SCL high before SDA low (for a repeated START

tsu(SCLH-SDAL)

4.7

0.6

µs

condition)

Hold time, SCL low after SDA low (for a START and a repeated

th(SCLL-SDAL)

0.6

µs

START condition)

tw(SCLL)

Pulse duration, SCL low

4.7

1.3

µs

tw(SCLH)

Pulse duration, SCL high

0.6

µs

tsu(SDAV-SCLH)

Setup time, SDA valid before SCL high

250

100(2)

th(SDA-SCLL)

Hold time, SDA valid after SCL low

0(3)

0.9(4)

µs

Pulse duration, SDA high between STOP and START

tw(SDAH)

4.7

1.3

µs

conditions

tr(SDA)

Rise time, SDA(5)

1000

20 + 0.1Cb

(6)

300

tr(SCL)

Rise time, SCL(5)

1000

20 + 0.1Cb

(6)

300

tf(SDA)

Fall time, SDA(5)

300

20 + 0.1Cb

(6)

300

tf(SCL)

Fall time, SCL(5)

300

20 + 0.1Cb

(6)

300

tsu(SCLH-SDAH)

Setup time, SCL high before SDA high (for STOP condition)

0.6

µs

tw(SP)

Pulse duration, spike (must be suppressed)

(6)

Capacitive load for each bus line

400

(1)

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. Also these pins are not 3.6 V-tolerant (their VIH cannot go above DVDDIO + 0.3 V).

(2)

A Fast-mode I2C-bus™ device can be used in a Standard-mode I2C-bus system, but the requirement tsu(SDA-SCLH)≥ 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 tr max + tsu(SDA-SCLH)= 1000 + 250 = 1250 ns

(according to the Standard-mode I2C-Bus Specification) before the SCL line is released.

(3)

A device must internally provide a hold time of at least 300 ns for the SDA signal (referred to the VIHmin of the SCL signal) to bridge the

undefined region of the falling edge of SCL.

(4)

The maximum th(SDA-SCLL) has only to be met if the device does not stretch the low period [tw(SCLL)] of the SCL signal.

(5)

The rise/fall times are measured at 30% and 70% of DVDDIO. The fall time is only slightly influenced by the external bus load (Cb) and

external pullup resistor. However, the rise time (tr) is mainly determined by the bus load capacitance and the value of the pullup resistor.

The pullup resistor must be selected to meet the I2C rise and fall time values specified.

(6)

Cb = total capacitance of one bus line in pF. If mixed with HS-mode devices, faster fall-times are allowed.

Figure 6-22. I2C Receive Timings

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