PCF8578 datasheet(8/46 Pages) NXP

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PCF8578_6

Product data sheet

Rev. 06 — 5 May 2009

8 of 46

NXP Semiconductors

PCF8578

LCD row/column driver for dot matrix graphic displays

Functional description

8.1 Display conﬁgurations

The PCF8578 row and column driver is designed for use in one of three ways:

• Stand-alone row and column driver for small displays (mixed mode)

• Row and column driver with cascaded PCF8579s (mixed mode)

• Row driver with cascaded PCF8579s (mixed mode and row mode)

[1]

Using 15 PCF8579s.

[2]

Using 16 PCF8579s.

In mixed mode, the device functions as both a row and column driver. It can be used in

small stand-alone applications, or for larger displays with up to 15 PCF8579s

(31 PCF8579s when two slave addresses are used). See Table 4 for common display

conﬁgurations.

In row mode, the device functions as a row driver with up to 32 row outputs and provides

the clock and synchronization signals for the PCF8579. Up to 16 PCF8579s can normally

be cascaded (32 when two slave addresses are used).

Timing signals are derived from the on-chip oscillator, whose frequency is determined by

the value of the resistor connected between pin OSC and pin VSS.

Five commands are available to conﬁgure and control the operation of the device.

Communication is made via a two-line bidirectional I2C-bus. The device may have one of

two slave addresses. The only difference between these slave addresses is the least

signiﬁcant bit, which is set by the logic level applied to SA0. The PCF8578 and PCF8579

have different subaddresses. The subaddress of the PCF8578 is only deﬁned in mixed

mode and is ﬁxed at 0111 100 (see Section 8.8.7 on page 19). The RAM may only be

accessed in mixed mode and data is loaded as described for the PCF8579.

Bias levels may be generated by an external potential divider with appropriate decoupling

capacitors. For large displays, bias sources with high drive capability should be used. A

typical mixed mode system operating with up to 15 PCF8579s is shown in Figure 5 (a

stand-alone system would be identical but without the PCF8579).

Table 4.

Possible display conﬁgurations

Applicatio

Multiplex rate Mixed mode

Row mode

Typical applications

Rows

Columns Rows

Columns

stand alone

1:8

small digital or

alphanumeric displays

1:16

1:24

1:32

with

PCF8579

1:8

8[1]

632[1]

× 4[2] 640[2]

alphanumeric displays

and dot matrix graphic

displays

1:16

16[1]

624[1]

× 2[2] 640[2]

1:24

24[1]

616[1]

24[2]

640[2]

1:32

32[1]

608[1]

32[2]

640[2]

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