PCF2104CUSLASH2 datasheet(7/56 Pages) MOTOROLA

7 / 56 page

1997 Dec 16

Philips Semiconductors

Product speciﬁcation

LCD controller/driver

PCF2104x

8.7

Address Counter (AC)

The Address Counter assigns addresses to the DDRAM

and CGRAM for reading and writing and is set by the

instructions ‘Set CGRAM address’ and

‘Set DDRAM address’. After a read/write operation the

Address Counter is automatically incremented or

decremented by 1. The Address Counter contents are

output to the bus (DB0 to DB6) when RS = logic 0 and

R/W = logic 1.

8.8

Display data RAM (DDRAM)

The DDRAM stores up to 80 characters of display data,

represented by 8-bit character codes. DDRAM locations

not used for storing display data can be used as general

purpose RAM. The basic DDRAM-to-display mapping

scheme is shown in Fig.2. With no display shift, the

characters represented by the codes in the first 12 or 24

RAM locations, starting at address 00 in line 1, are

displayed. Subsequent lines display data starting at

addresses 20, 40, or 60 Hex. Figures 3 and 4 show the

DDRAM-to-display mapping scheme when the display is

shifted.

The address range for a 1-line display is 00 to 4F; for a

2-line display from 00 to 27 (line 1) and 40 to 67 (line 2);

for a 4-line display from 00 to 13, 20 to 33, 40 to 53 and

60 to 73 for lines 1, 2, 3 and 4 respectively. For 2 and

4-line displays the end address of one line and the start

address of the next line are not consecutive. When the

display is shifted each line wraps around independently of

the others (see Figs 3 and 4).

When data is written to the DDRAM wrap-around occurs

from 4F to 00 in 1-line mode and from 27 to 40 and

67 to 00 in 2-line mode; from 13 to 20, 33 to 40, 53 to 60

and 73 to 00 in 4-line mode.

8.9

Character generator ROM (CGROM)

The character generator ROM generates 240 character

patterns in 5

× 8 dot format from 8-bit character codes.

Figures 5 and 6 show the character sets currently

available.

8.10

Character generator RAM (CGRAM)

Up to 16 user-defined characters may be stored in the

character generator RAM. The CGROM and CGRAM use

a common address space, of which the first column is

reserved for the CGRAM (see Fig.5). Figure 8 shows the

addressing principle for the CGRAM.

8.11

Cursor control circuit

The cursor control circuit generates the cursor (underline

and/or character blink as shown in Fig.9) at the DDRAM

address contained in the Address Counter. When the

Address Counter contains the CGRAM address the cursor

will be inhibited.

8.12

Timing generator

The timing generator produces the various signals

required to drive the internal circuitry. Internal chip

operation is not disturbed by operations on the data buses.

8.13

LCD row and column drivers

The PCF2104x contains 32 row and 60 column drivers,

which connect the appropriate LCD bias voltages in

sequence to the display, in accordance with the data to be

displayed. The bias voltages and the timing are selected

automatically when the number of lines in the display is

selected. Figures 10 and 11 show typical waveforms.

In the 1-line mode (1 : 16) the row outputs are driven in

pairs: R1/R17, R2/R18 for example. This allows the output

pairs to be connected in parallel, thereby providing greater

drive capability.

Unused outputs should be left unconnected.

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