7220 datasheet(101/303 Pages) RENESAS

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2-74

7220 Group User’s Manual

FUNCTIONAL DESCRIPTION

2.11 CRT display function

2.11.1 Display position

The display positions of characters are specified in units called a “block”. There are 2 blocks, block 1 and

block 2. Up to 24 characters can be displayed in 1 block (refer to “2.11.3 Memory for display”).

The display position of each block in both horizontal and vertical directions can be set by software.

The horizontal direction is common to all blocks, and is selected from 64-step display positions in units of

4 TC (TC = oscillation cycle for display).

The display position in the vertical direction is selected from 128-step display positions for each block in

units of 4 scanning lines. The display position in the vertical direction is determined by counting the

horizontal sync signal (HSYNC).

At this time, it starts to count the rising edge (falling edgeV) of HSYNC signal from after about 1 machine cycle

of rising edge (falling edgeV) of VSYNC signal. So interval from rising edge (falling edge ) of HSYNC signal

needs enough time (2 machine cycles or more) for avoiding jitter.

V:The polarity of HSYNC and VSYNC signals can select by the CRT port control register (address 00EC16).

When clearing corresponding bits to “0,” positive polarity is selected, when setting to “1,” negative

polarity is selected. Refer to “2.11.7 CRT output pin control” for detail.

Fig. 2.11.4 Count method of synchronous signal

When bits 0 and 1 of the CRT port control register (address 00EC16)

are set to “1” (negative polarity)

Note 1: The vertical position is determined by counting falling

edge of HSYNC signal after rising edge of VSYNC control

signal in the microcomputer.

2: At f(XIN) = 8 MHz

3: Do not generate falling edge of HSYNC signal near rising edge

SYNC

control signal in microcomputer to avoid jitter.

4: Pulse width of VSYNC and of HSYNC signals needs 8 machine

VSYNC signal input

VSYNC control signal

in microcomputer

Period of counting

HSYNC signal

HSYNC signal input

0.125

µs to 0.25 µs (See note 2)

(See note 3)

234

Not count

↑

8 machine cycles or more (See note 4)

8 machine cycles or more

(See note 4)

cycles or more.

of V

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