PCF8820U Philips Semiconductors, PCF8820U Datasheet - Page 17

• Manufacturer Part Number: PCF8820U
• Description: 67 x 101 Grey-scale/ECB colour dot matrix LCD driver
• Manufacturer: Philips Semiconductors

Philips Semiconductors
7.18.5
The PCF8820 is a slave transmitter/receiver. If data is to
be read from the device, the SDA_OUT output must be
used.
Before any data is transferred over the I
destination device is addressed first (see Fig.15).
The PCF8820 has four 7-bit slave addresses reserved:
0111 100, 0111 101, 0111 110 and 0111 111. The two
least significant bits of the slave address are set by
connecting slave address inputs SA1 and SA0 to either
V
A write sequence (see Fig.17) is initiated with a START
condition (S) from the I
the slave address. Only the addressed slave
acknowledges. After acknowledgement, one or more
command words follow which define the status of the
addressed slave.
A command word consists of a control byte (see Fig.16)
defining ‘continuation’ bit Co and ‘register selection’
bit RS, plus a data byte. The last control byte is indicated
by resetting bit Co = 0. The control and data bytes are also
acknowledged by all addressed slaves on the bus.
Depending on the setting of bit RS in the last control byte,
either a series of display data bytes or command data
bytes may follow.
If bit RS = 1, the data bytes are stored as display data in
the DDRAM at the address specified by the data pointer.
The data pointer is automatically incremented.
If bit RS = 0, the data byte is interpreted as a command
byte to be decoded and the device will be set according to
the received commands.
2000 Dec 07
handbook, full pagewidth
SS1
67 101 Grey-scale/ECB colour dot matrix
LCD driver
(logic 0) or V
S 0 1 1 1 1
I
2
C-
slave address
BUS PROTOCOL
DD1
S
A
1
acknowledgement
(logic 1).
from PCF8820
2
S
A
0
C-bus master which is followed by
R/W
0 A
Fig.17 Write sequence: master transmits bytes to slave receiver.
Co
1
RS
control byte
2
C-bus, the
acknowledgement
from PCF8820
2n
A
0 bytes
data byte
17
acknowledgement
Only the addressed PCF8820 acknowledges after each
byte is received. The I
condition (P) at the end of the transmission.
from PCF8820
condition
START
MGU185
A
Co
S
0
RS
continuation
0
Co RS
bit
control byte
selection
1 byte
register
1
Fig.15 Slave address.
bit
Fig.16 Control byte.
acknowledgement
slave address
1
from PCF8820
X
2
C-bus master issues a stop
1
control byte
A
X
1
address
X
slave
bit 1
SA1
data byte
m
MGT125
address
X
slave
SA0
bit 0
0 bytes
Product specification
X
read/write
acknowledgement
R/W
MGT124
from PCF8820
PCF8820
acknowledge
bit
data pointer
X
update
bit
A
A P