PCF8820 datasheet(18/60 Pages) PHILIPS

18 / 60 page

2000 Dec 07

Philips Semiconductors

Product speciﬁcation

× 101 Grey-scale/ECB colour dot matrix

LCD driver

PCF8820

For a read sequence (see Fig.18), the addressed

PCF8820 will immediately start to output the requested

data until a NOT acknowledge is transmitted by the

master. Before the read access, the user has to set bit RS

to the appropriate value by a preceding write access. The

sequence should be terminated by a STOP condition

when no further access is required, or by a RE-START

condition if further access is required.

7.18.6

COMMAND DECODER

The command decoder identifies command words

received via the I2C-bus.

Bit 7 of the control byte is named bit Co (see Fig.16):

• Bit Co = 1 indicates that only one command byte or

DDRAM data byte will follow next

• Bit Co = 0 indicates that a stream of command bytes or

DDRAM data bytes will follow next depending on last

status of bit RS.

Bit 6 of a control byte is named bit RS:

• Bit RS = 1 indicates that another DDRAM data byte will

follow next

• Bit RS = 0 indicates that another command byte will

follow next.

The definition of bits Co and RS is shown in Table 1.

7.18.7

DISPLAY DATA BYTE

A display data byte for grey-scale is shown in Fig.19.

MGT126

S 01111

acknowledgement

from PCF8820

not acknowledgement

from master

temperature

readout value

slave address

R/W

STOP condition

Fig.18 Read sequence: master receives bytes

from slave transmitter status register.

MGT127

LSB

pixel 3

pixel 2

pixel 1

pixel 0

MSB

LSB

MSB

LSB

MSB

LSB

MSB

DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0

MSB

LSB

Fig.19 Grey-scale display data byte.

Table 1

Deﬁnition of bits Co and RS

BIT

VALUE

ACTION

last control byte to be sent; only a stream of data bytes are allowed to follow; this stream may

only be terminated by a STOP or RE-START condition

another control byte will follow the data byte unless a STOP or RE-START condition is

received

data byte will be decoded and used to set up the device

data byte will return the sensor temperature read-out

data byte will be stored in the DDRAM

RAM read-back (not supported)

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