STV9936S datasheet(29/48 Pages) STMICROELECTRONICS

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STV9936P/S

RAM Specification

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

Figure 5, 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 19),

leaving 22 blocks of 32 characters for character codes (704 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 22.

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 30: Window Sizes

Window

Size

Window 1

Window 2

Window 3

Window 4

Total

Table 31: 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]

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