MC68HC705T16 MOTOROLA [Motorola, Inc], MC68HC705T16 Datasheet - Page 73

• Manufacturer Part Number: MC68HC705T16
• Description: High-density complementary metal oxide semiconductor (HCMOS) microcontroller unit
• Manufacturer: MOTOROLA [Motorola, Inc]

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Character Features
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9.3
Characters are stored in a 128-character ROM and a 16-character RAM. The 128 pairs of
character registers are equally allocated for the 4 row buffers, each have 32 pairs. Each pair of
character registers consists of the Character Code register and the Character Attribute register.
The Character Code register selects the particular character from the character
ROM/EPROM/RAM. The Character Attribute register selects the color, background, and blinking
features for that selected character.
9.3.1
OSD character RAM is a dual ported RAM, consisting of 16x(16x16)/8=512 bytes of RAM;
located from $0400 to $05FF. Upon reset, the content of character RAM is random. Every entry
of this 16-entry character RAM occupies 32 consecutive memory bytes, always starting at even
addresses. Users can read and write any byte at any time. OSD can only read the character RAM.
Figure 9-1 shows the memory map of one entry of the 16-entry OSD character RAM.
If 12x16 character dot matrix is selected, bit 3 to bit 0 of all low order bytes at the right-hand side
of Figure 9-1 will not be used for display.
9.3.2
The memory arrangement of OSD character ROM/EPROM is the same as that of character RAM.
Character ROM/EPROM is not readable to the CPU in user mode. OSD character ROM is located
from $8000 to $8FFF. Three characters in the Character ROM are fixed, and cannot be changed.
They are shown in Figure 9-2.
MC68HC05T16
Interrupt on the leading edge of vertical flyback signal
128-character ROM/EPROM plus 16-character RAM. Character RAM is dual ported
Character attribute is on per character basis
Individually controllable character background
Character blinking with four blinking rates
Characters
Character RAM
Character ROM/EPROM
ON-SCREEN DISPLAY
MOTOROLA
TPG
9-3
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