PCF8811USLASH2DASLASH1 datasheet(28/81 Pages) NXP

28 / 81 page

PCF8811_4

Product data sheet

Rev. 04 — 27 June 2008

28 of 81

NXP Semiconductors

PCF8811

80 x 128 pixels matrix LCD driver

10.1.2 Read mode (only extended command set)

The read mode of the interface means that the microcontroller reads data from the

PCF8811. To do so, the microcontroller ﬁrst has to send a command (the read status

command) and then the PCF8811 will respond by transmitting data on the SDO line. After

that, SCE is required to go HIGH; see Figure 19.

The PCF8811 samples the SDATA data on rising SCLK edges, but shifts SDO data on

falling SCLK edges. So, the microcontroller is supposed to read SDO data on rising SCLK

edges.

After the read status command has been sent, the SDATA line must be set to 3-state not

later then the falling SCLK edge of the last bit; see Figure 19.

Serial interface timing diagrams are shown in Section 16.2.

10.2 Serial interface (3-line)

The serial interface is also a 3-line bidirectional interface for communication between the

microcontroller and the LCD driver chip. The 3 lines are:

• SCE (chip enable)

• SCLK (serial clock)

• SDATA (serial data)

The PCF8811 is connected to the SDA of the microcontroller by two lines: SDATA (data

input) and SDO (data output) which are connected together.

10.2.1 Write mode

The write mode of the interface means that the microcontroller writes commands and data

to the PCF8811. Each data packet contains a control bit (D/C) and a transmission byte. If

D/C is LOW, the following byte is interpreted as a command byte. The instruction set is

shown in Table 10. If D/C is HIGH, the following byte is stored in the display data RAM.

After every data byte the address counter is incremented automatically. Figure 20 shows

the general format of the write mode and the deﬁnition of the transmission byte.

Fig 19. Read mode SPI 3-line and 4-line

RES

SCLK

SDATA

DB7 DB6 DB5 DB4

DB2

DB3

DB1 DB0

SDO

instruction

DB2

DB7 DB6 DB5

DB4 DB3

DB1 DB0

mgw748

read out data

SCE

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