pcf85132 NXP Semiconductors, pcf85132 Datasheet - Page 39

• Manufacturer Part Number: pcf85132
• Description: Pcf85132 Lcd Driver For Low Multiplex Rates
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF85132
Product data sheet
12.3 Cascaded operation
In large display configurations, up to 8 PCF85132 can be distinguished on the same
I
I
Table 20.
When cascaded PCF85132 are synchronized, they can share the backplane signals from
one of the devices in the cascade. Such an arrangement is cost-effective in large LCD
applications since the backplane outputs of only one device need to be through-plated to
the backplane electrodes of the display. The other PCF85132 of the cascade contribute
additional segment outputs but their backplane outputs are left open-circuit (see
Figure
For display sizes that are not multiple of 640 elements, a mixed cascaded system can be
considered containing only devices like PCF85132 and PCF85133. Depending on the
application, one must take care of the software commands compatibility and pin
connection compatibility.
The SYNC line is provided to maintain the correct synchronization between all cascaded
PCF85132. This synchronization is guaranteed after the Power-On Reset (POR). The
only time that SYNC is likely to be needed is if synchronization is accidentally lost (e.g. by
noise in adverse electrical environments, or by the definition of a multiplex mode when
PCF85132 with different SA0 levels are cascaded). SYNC is organized as an input/output
pin; the output selection being realized as an open-drain driver with an internal pull-up
resistor. A PCF85132 asserts the SYNC line at the onset of its last active backplane signal
and monitors the SYNC line at all other times. Should synchronization in the cascade be
lost, it will be restored by the first PCF85132 to assert SYNC. The timing relationship
between the backplane waveforms and the SYNC signal for the various drive modes of
the PCF85132 are shown in
When using an external clock signal with high frequencies (f
recommended to have an external pull-up resistor between pin SYNC and pin V
Table
When using it in a cascaded configuration, care must be taken not to route the SYNC
signal to close to noisy signals.
The contact resistance between the SYNC pads of cascaded devices must be controlled.
If the resistance is too high, the device will not be able to synchronize properly. This is
particularly applicable to COG applications.
resistance.
Cluster
1
2
2
2
C-bus by using the 2-bit hardware subaddress (A0 and A1) and the programmable
C-bus slave address (SA0).
19). This resistor should be present even when no cascading configuration is used!
29).
Addressing cascaded PCF85132
All information provided in this document is subject to legal disclaimers.
Bit SA0
0
1
Rev. 1 — 23 November 2010
Figure
31.
Pin A1
0
0
1
1
0
0
1
1
Table 21
shows the limiting values for contact
LCD driver for low multiplex rates
Pin A0
0
1
0
1
0
1
0
1
clk(ext)
> 4 kHz) it is
PCF85132
© NXP B.V. 2010. All rights reserved.
Device
0
1
2
3
4
5
6
7
DD
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(see