4 vram – NEC PD17062 User Manual
Page 246
246
µ
PD17062
20.4 VRAM
VRAM is the memory that holds data used to select a picture pattern that the IDC displays on a screen such
as a TV screen. In the
µ
PD17062, the VRAM data is allocated at BANK1 and BANK2 in data memory. One VRAM
data item (8 bits) is held at two adjoining addresses (even and odd address).
BANK1 and BANK2 are each mapped at 112 nibbles of data memory (total of 224 nibbles, or 224
×
4 bits).
That is, up to 112 VRAM data items can be specified.
Fig. 20-1 VRAM Configuration
VRAM data consists of 8 bits. Of the 8 bits, the upper 2 bits are the ID field. The ID field indicates the type
of VRAM data. The lower 6 bits are the data field. The data field contains the display data or control data.
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
0
1
2
3
4
5
6
VRAM data
Column address
Row address
Even
address
Odd
address
4 bits
4 bits
(2 data memory locations)