On Sat, Apr 14, 2001 at 12:27:36PM -0500, Scott Dattalo wrote:
>
> Too bad the 877 does not have enough internal RAM storage...
>
In fact it has, if someone is going to use only the character mode.
The display may be divided into 4 rows, 64 characters each (16x8 character
cell). So there is only 256 bytes of RAM needed (I think it should be
divided into four buffers - one for each row located in different banks,
eg.: 0x20-0x5f row 0
     0xa0-0xdf row 1
     0x120-0x15f row 2
     0x1a0-0x1df row 3

The character generator may be located in FLASH memory (it requires 4kB of
memory for 256 characters, only the lower 8 bits of each word will be used).
To make decoding easier, it should be allocated as follows:
byte_address = Start_of_CGROM + 256 * number_of_character_scan_line + char_code
Start_of_CGROM should be 256 bytes alligned

However I'd like to add communication with the PC keyboard, and
bidirectional RS-232 communication with the PC (the whole thing should be a
small RS232 terminal), and it's getting very difficult to achieve the 70Hz
LCD refresh ratio :-(.

--
                        Wojtek Zabolotny
                        wzab@ise.pw.edu.pl

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