L6238 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6238' PDF : 35 Pages View PDF
L6238
Figure 30 is the timing diagram for writing to the
serial port. This diagram indicates the typical
waveforms at the serial port and how they relate
to one another when the PORT DISABLE pin is
used. Two consecutive write cycles with key tim-
ing parameters are illustrated.
To initiate the write cycle, the STROBE and R/W
signals are first brought low. After a minimum set-
up time, Tos, the PORT DISABLE pin is set low.
The clocking of the data can begin after a mini-
mum settling time, Tsettle has passed. The data is
clocked into the register on the falling edge of the
PORT CLOCK. After the 16th clock cycle and
wait time Tcsw a strobe signal causes the data to
be transferred to the 16-bit latch.
Additional timing parameters that are relevant
concern the timing of the clock signal relative to
the data stream. The time Tds is the data set up
Figure 30: Write Timing Diagram.
time, where the data must be stable before the
falling edge of the clock. The Data Hold time, Tdh,
is the minimum time that the data must be valid
after the rising edge of the clock pulse.
The waveforms associated with reading from the
serial port are similar to the write mode. The main
difference is in the timing of the strobe pulse.
Since there is a single port for both read and
write, the strobe signal, in conjunction with the
R/W signal insures proper data stream flow.
Referring to figure 31, the read mode is initiated
by first asserting the R/W line high, while holding
the strobe line low. The PORT DISABLE pin is
then brought low. A pulse is now sent to the
strobe pin that transfers the data on the Status
Bus to the Shift Register. The falling edge of the
strobe cannot occur earlier than the minimum set-
tling time, Tsettle. The data is shifted out on the
Figure 31: Read Timing Diagram.
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