LM1247 Address Map

CHARACTER ROM

The 512 font characters from 0x0000 to 0x7FFF can be read from ROM by addressing the individual pixel rows of the desired

character. Since the characters have 12 columns, it takes two bytes to read a given row of pixels within one character. Since the

characters have 18 rows, a total of 36 bytes are needed to read the entire character. The 16 bit address for reading a row of pixels

is formed as follow:

where: N = bank number (0x0

≤ N ≤ 0x7)

I = Character Index within its respective bank (0x00

≤ I ≤ 0x3F)

R = row of pixels within the character (0x00

≤ R ≤ 0x11)

H = 0 for low byte, 1 for high byte

Note that bit 0 of the Character Font Access Register, 0x8402, needs to be set to 0 to read the 2-color fonts. In order to read the

four-color fonts, two complete reads are needed. Set bit 0 of the Character Font Access Register, 0x8402, toa0to read the least

significant plane and toa1to read the most significant plane. See Table 4.

TABLE 4. Character ROM Addressing

Address Range

R/W

Description

0x8402[0]

N

0x0000–0x2FFF

R

These are the first 3 banks of two-color, read-only ROM character

fonts. There are 192 total characters in this range.

0

0x0

0x1

0x2

0x3000–0x3FFF

R

This is bank 3 of four-color, read-only ROM character fonts. There

are 64 total characters in this range.

0/1

0x3

0x4000–0x6FFF

R

These are banks 4, 5 and 6 of two-color read-only ROM character

fonts. There are 192 characters in this range.

0

0x4

0x5

0x6

0x7000–0x7FFF

R

This is bank 7 of four-color, read-only ROM character fonts. There

are 64 total characters in this range.

0/1

0x7

When read back, the low byte will contain the first eight pixels of the row with data bit 0 corresponding to the left most bit in the

pixel row. The high byte will contain the remaining four pixels in the least significant nibble. The remaining 4 bits, shown as “X”,

are “don’t care” bits, and should be discarded. Bit 3 of the high byte corresponds to the right most pixel in the pixel row. This is

shown in Table 5.

20048439

FIGURE 24. I

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