HD64645 Datasheet, PDF (32/50 Pages) Hitachi Semiconductor – LCTC (LCD Timing Controller)

HD64645/64646
Internal Registers
The HD64645/HD64646 has one address register and fourteen data registers. In order to select one out of
fourteen data registers, the address of the data register to be selected must be written into the address
register. The MPU can transfer data to/from the data register corresponding to the written address.
To be software compatible with the CRTC (HD6845), registers R2–R8, R16, and R17, which are not
necessary for an LCD are defined as invalid for the LCTC.
Address Register (AR)
AR register (Figure 22) specifies one out of 14 data registers. Address data is written into the address
register when RS is low. If no register corresponding to a specified address exists, the address data is
invalid.
Horizontal Total Characters Register (R0)
R0 register (Figure 23) specifies a horizontal scanning period. The total number of horizontal characters
less 1 must be programmed into this 8-bit register in character units. Nht indicates the horizontal scanning
period including the period when the CPU occupies memory (total number of horizontal characters minus
the number of horizontal displayed characters). Its units are, then, converted from time into the number of
characters. This value should be specified according to the specification of the LCD system to be used.
Note the following restrictions
Nhd +
16
m
≤ Nht + 1
Mode No.
m
5, 9
1
1, 6, 7, 8, 10, 11, 12, 13
2
2, 3, 4
4
Horizontal Displayed Characters Register (R1)
R1 register (Figure 24) specifies the number of characters displayed per row. The horizontal character
pitches are 8 bits for normal character display and 16 dots for wide character display and graphic display.
Nhd must be less than the total number of horizontal characters.
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