PCF8820U Philips Semiconductors, PCF8820U Datasheet - Page 18

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

Philips Semiconductors
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
The command decoder identifies command words
received via the I
Bit 7 of the control byte is named bit Co (see Fig.16):
Bit 6 of a control byte is named bit RS:
The definition of bits Co and RS is shown in Table 1.
7.18.7
A display data byte for grey-scale is shown in Fig.19.
Table 1 Definition of bits Co and RS
2000 Dec 07
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 RS = 1 indicates that another DDRAM data byte will
follow next
Bit RS = 0 indicates that another command byte will
follow next.
67 101 Grey-scale/ECB colour dot matrix
LCD driver
BIT
RS
Co
C
D
OMMAND DECODER
ISPLAY DATA BYTE
VALUE
2
0
1
0
1
C-bus.
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)
18
Fig.18 Read sequence: master receives bytes
S 0 1 1 1 1
ACTION
slave address
MSB
DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
Fig.19 Grey-scale display data byte.
LSB
from slave transmitter status register.
P3
pixel 3
MSB
P3
S
A
1
acknowledgement
from PCF8820
LSB
S
A
0
P2
R/W
pixel 2
1 A
MSB
P2
LSB
readout value
P1
temperature
pixel 1
MSB
P1
Product specification
not acknowledgement
LSB
P0
from master
PCF8820
pixel 0
STOP condition
MGT127
LSB
MSB
A P
P0
MGT126