STV9937 datasheet(27/49 Pages) STMICROELECTRONICS

27 / 49 page

27/49

STV9937

RAM Specification

The user must reserve a memory space for the largest window. According to the example shown in

Figure 6, the total number of characters/spaces are:

For example, to change the size of Window 3 from 3 rows of 6 characters to 5 rows of 4 characters,

the resulting size is 20 characters. The number of rows increases and the number of characters per

row decreases. The required memory is at least 20 characters.

Note:

A space is considered as being a character.

The memory allocation is made by blocks of 32 characters.

The maximum size of a window is 16 rows of 32 characters, or 512 characters. This corresponds to

16 blocks of 32 characters.

1 block is reserved for the color-boxes (see Chapter 4: Character Specifications on page 20),

leaving 20 blocks of 32 characters for character codes (640 characters maximum).

The RAM allocation for each window is coded in bits ALWi[3:0]. Window 4 memory allocation uses

the remaining memory space.

The number of memory blocks allocated for window “i” is (ALWi +1), the range of allocation is 1 to

16 blocks of 32 characters. The total number of blocks is 20.

Note:

If the user changes only 1 window allocation, the RAM addresses of the following windows change.

Consequently we advise you to write the allocation when the windows are not displayed to avoid

false images.

Table 29: Window Sizes

Window

Size

Window 1

Window 2

Window 3

Window 4

Total

Table 30: Window RAM Allocation

FWR

FAC

Default

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

80h

09h

39h

ALW2[3:0]

ALW1[3:0]

80h

0Ah

ALW3[3:0]

STV9937 Fiches technique(PDF) 27 Page - STMicroelectronics

STV9937 Fiches technique(HTML) 27 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

Fiches technique Télécharger

Lien URL