CDCE421RGET datasheet(6/24 Pages) TI1

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Enter Programming Mode

SDATA

DATA

SDATA

DELAYED

T0042-05

EEPROM PROGRAMMING

CDCE421

SCAS842B – APRIL 2007 – REVISED JANUARY 2009..................................................................................................................................................... www.ti.com

Figure 3 shows the timing behavior of data to be written into SDATA. The sequence shown is 00 1100. If the high

period is as short as t1, this is interpreted as 0. If the high period is as long as t3, this is interpreted as a 1. This

behavior is achieved by shifting the incoming signal SDATA by time t5 into signal SDATA_DELAYED. As can be

seen in Figure 3, SDATA_DELAYED can be used to latch (or strobe) SDATA. The timing specifications for t1–t7,

tr, and tf are shown in Figure 3.

MIN

TYP

MAX

UNIT

fSDATACLK

Repeat frequency of programming

kHz

LOW signal: high-pulse duration

0.2 t

LOW signal: low-pulse duration while entering programming sequence

0.8 t

LOW signal: low-pulse duration while programming bits

0.8 t

HIGH signal: high-pulse duration

0.8 t

HIGH signal: low-pulse duration while entering programming sequence

0.2 t

HIGH signal: low-pulse duration while programming bits

0.2 t

Time-out during Entering Programming Mode and Enter Read Back Mode.

High-pulse or low-pulse duration each must be less than this time; otherwise,

µs

time-out will result.

CE-high time before first SDATA can be clocked in

3 t

tr and tf

Rise Time and Fall Time

t = 1 / fSDATACLK

Figure 3. SDATA/CE Timing

Load all the registers in RAM by writing Word0 through Word5, and after going back to State 2, then going to

State 3 (programming EEPROM, no locking) or State 4 (programming EEPROM with locking), the contents of

Word0–Word5 are saved in the EEPROM. Wait 10 ms in State 3 or State 4 when programming the EEPROM

before moving to State 2 (the idle state).

NOTE:

When writing to the device for functionality testing and verification via the serial bus,

only the RAM is being accessed.

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