µPD16662
Data bus
The byte data lined up on the data bus is based on the Little Endian - an NEC/Intel-series bus.
1. 16 bit data bus (BMODE = L)
• Bytes (8 bytes) access
Addresses proceed as →
shown on right.
• Words (16 bits) access
D0 to D7
00000H
00002H
00004H
:
:
:
D8 to D15
00001H
00003H
00005H
:
:
:
Addresses proceed as →
shown on right.
D0 to D7
00000H
00002H
00004H
:
:
:
D8 to D15
For the access from the system to be performed in units of words (16 bits), or of bytes (8 bytes), the /UBE (high
byte enable) and A0 are used to show whether valid data are in the bytes of either (or both) of D0 to D7 and D8 to
D15.
/CS
/OE
/WE
H
X
X
L
L
H
L
H
L
L
H
H
L
X
X
Remark X : Don’t Care
Hi-Z : High impedance
/UBE
X
L
L
H
L
L
H
X
H
A0
MODE
I/ O
D0 to D7
D8 to D15
X
Not Selected
Hi-Z
Hi-Z
L
Read
Dout
H
Hi-Z
L
Dout
L
Write
Din
H
X
L
Din
X
Output disable
Hi-Z
H
Hi-Z
Dout
Dout
Hi-Z
Din
Din
X
Hi-Z
Hi-Z
6