7220 datasheet(178/303 Pages) RENESAS

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APPLICATION

5.1 Example of multi-line display

5-5

7220 Group User’s Manual

(3)

CRT interrupt processing routine

The CRT interrupt processing routine executes the display character data setup routine for each line,

in order to perform multi-line display. The line to be displayed is determined by the line counter value.

Fig. 5.1.5 Flowchart of CRT interrupt processing routine

CRT interrupt processing routine

← Specify jump destination by

Line counter value

RETURN

Line counter +1

Line counter =12

Line counter

← “0”

Save the value of Line counter

in internal RAM

Pop registers X, Y, A

ICON1

ICON2

=12

≠12

←“0”

←ICON1

←ICON2

←“001000012”

←“000000002”

←“0”

CRT_ICON1

CRT_ICON2

ICON1 (address 00FE 16)

ICON2 (address 00FF 16)

Push registers X, Y, A

ICON1, ICON2:

CS :

HR :

Line counter :

CV1,CV2 :

CRT_ICON1, CRT_ICON2 :

A :

X :

Y :

T :

D :

Interrupt control registers 1, 2

Character size register

Horizontal position register

Counter RAM for line counting

Vertical position registers 1, 2

Back up RAM for interrupt control

registers 1, 2 during CRT interrupt

Accumulator

Index register X

Index register Y

X modified operation mode flag

Decimal operation mode flag

←Disable all interrupts

Note: The multiple interrupt priority of

SYNC

> CRT

←“1”

←CRT_ICON1

←CRT_ICON2

←Pop ICON 1 and 2 contents during

interrupt (Refer to “5.1.7 (2)”)

← Enable Timer 1 interrupt and

VSYNC interrupt

Line counter = 0

= 1

Set CS, HR

Block 1 display RAM

←

Display character of block 1 (the 1st line)

Character color of block 1 (the 1st line)

CV1

← Vertical display start position

of the 1st line (block 1)

Set CS, HR

Block 2 display RAM

←

Display character of block 2 (the 2nd line)

Character color of block 2 (the 2nd line)

= 11

Set CS, HR

Block 2 display RAM

←

Display character of block 2 (the 12th line)

Character color of block 2 (the 12th line)

CV2

← Vertical display start position

of the 2nd line (block 2)

CV2

← Vertical display start position

of the 12th line (block 2)

CRT

this system is as below.

Timer 1 > V

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