Effect

This instruction can be used in

• reading mode for all supported screen modes : it returns then the first VRAM address for a specific purpose

In SCREEN 5 to 8 and 10 to 12, you'll get the offset value from the starting address of the active page.

• writing mode, which works only for table numbers from 0 to 19, corresponding to SCREEN 0 to 3 : it allows then to change the first VRAM address for a specific purpose. VDP registers will be updated automatically. The value should be possible for VDP to implement and must be less than &H4000 otherwise Illegal function call-error will be generated.

Note that a change in table numbers from 10 to 14 for SCREEN 2 will also change the corresponding VRAM address for SCREEN 4.

Syntax

BASE(<TableNumber>)

<TableNumber> that returns corresponding VRAM address can be calculated with formula 5 * SCREEN MODE + PURPOSE. All the practically usable values are listed in a table below.

(*) SCREEN 1 is a text screen, but the charset can be filled with game graphics and sprites can also be used
(**) SCREEN 9 is a text screen, initially conceived for Korean characters, and using graphic mode SCREEN 5 or SCREEN 6

The Sprite Color Table, available only on MSX2 and higher and used for the sprites type 2 on screens 4 to 8 and 10 to 12 is located "strictly above" the sprite attribute table, having base address of sprite attribute table minus 512 (200 in hexadecimal).

Examples

PRINT BASE(2)

2048

10 SC=PEEK(&HFCAF) ' Current screen mode (= 0/1 for text)
11 A=ASC("!")*8+BASE(SC*5+2) ' VRAM address for "!"-font outlook
12 FOR I=0 TO 7:READ D$:VPOKEA+I,VAL("&B"+D$):NEXT I
13 'New look (Note: Two last columns are not in use in screen 0)
14 DATA 00110000
15 DATA 01111000
16 DATA 01111000
17 DATA 00110000
18 DATA 00000000
19 DATA 00110000
20 DATA 00110000
21 DATA 00000000

10 COLOR 15,4,7: KEYOFF
20 BASE(5)=BASE(6)
30 SCREEN 1
40 FOR I = 0 TO 38
50 PRINT"A TEST OF THE BASE COMMAND"
60 FOR J = 0 TO 100
70 NEXT J
80 NEXT I
90 LIST
100 END

Returned default values (after boot)

Name Table

Color Table

Pattern Table

Sprite Attribute Table

Sprite Pattern Table

Sprite Color Table

References

• VDP Ports
• VDP Registers

Related to

SCREEN, VDP(), VPOKE, VPEEK

Compatibility

MSX-BASIC 1.0 or higher