PCF2119FUSLASH2SLASHF2 datasheet(29/79 Pages) NXP

29 / 79 page

PCF2119X_5

Product data sheet

Rev. 05 — 13 August 2009

29 of 79

NXP Semiconductors

PCF2119x

LCD controllers/drivers

The previous Set_CGRAM or Set_DDRAM command determines if data is written into

CGRAM or DDRAM. After writing, the address counter automatically increments or

decrements by 1, in accordance with the Entry_mode_set (see Section 10.2.2.3). Only bit

4 to bit 0 of CGRAM data are valid, bit 7 to bit 5 are ‘don’t care’.

10.2.2 Standard instructions (bit H = 0)

10.2.2.1

Clear_display

Clear_display: writes usually the character code 20h (blank pattern) into all DDRAM

addresses except for the character sets ‘R’ and ‘V’ where the character code 20h is not a

blank pattern.

In addition Clear_display

• sets the DDRAM address counter to logic 0

• returns the display to its original position, if it was shifted. Thus, the display

disappears and the cursor or blink position goes to the left edge of the display

• sets entry mode bit I_D = 1 (increment mode); bit S of entry mode does not change

The instruction Clear_display requires extra execution time. This may be allowed by

checking the busy ﬂag bit BF or by waiting until the 165 clock cycles have elapsed. The

latter must be applied where no read-back options are foreseen, as in some

Chip-On-Glass (COG) applications.

Remark: When using the character sets ‘R’ or ‘V’, where the character code 20h is not the

blank pattern, the following alternative instruction set has to be used:

1. Switch display off (Display_ctl, bit D = 0).

2. Write a blank pattern into all DDRAM addresses (Write_data).

3. Switch display on (Display_ctl, bit D = 1).

10.2.2.2

Return_home

Return_home: Sets the DDRAM address counter to logic 0 and switches a shifted

display back to an unshifted state. The DDRAM content remain unchanged. The cursor or

blink position goes to the left of the ﬁrst display line. Bit I_D and bit S of the

Entry_mode_set instruction remain unchanged.

Table 16.

Clear_display bit description

Bit

Symbol

Value

Description

see Table 10

R/W-

7 to 0

00000001

ﬁxed value

Table 17.

Return_home bit description

Bit

Symbol

Value

Description

see Table 10

R/W-

7 to 0

00000010

ﬁxed value

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