Page 14 Epson Research and Development
Vancouver Design Center
S1D13505 Interfacing to the NEC VR4121 Microprocessor
X23A-G-011-04 Issue Date: 01/02/05
4.4 Memory Mapping and Aliasing
The NEC VR4121 provides the internal address decoding required by an external LCD
controller. The physical address range from 0A00 0000h to 0AFF FFFFh (16M bytes) is
reserved for use by an external LCD controll er (e.g. S1D13505).
The S1D13505 supports up to 2M bytes of display buffer. The NEC VR4121 address line
ADD21 (connected to M/R#) is used to select between the S1D13505 display buffer
(ADD21=1) and the S1D13505 internal registers (ADD21=0). NEC VR4121 address lines
ADD[23:22] are ignored, thus the S1D13505 is aliased four times at 4M byte interval s over
the LCD controller address range. Address lines ADD[25:24] are set at 10b and never
change while the LCD controller is being a ddressed.