MB90480/485 Series
19. Chip Select Function Description
The chip select module generates a chip select signals, which are used to facilitate connections to external
memory devices. The MB90480/485 series has four chip select output pins, each having a chip select area
register setting that specifies the corresponding hardware area and select signal that is output when access to
the corresponding external address is detected.
• Chip select function features
The chip select function uses two 8-bit registers for each output pin. One of these registers (CARx) is able to
detect memory areas in 64 Kbytes units by specifying the upper 8-bit of the address for match detection. The
other register (CMRx) can be used to expand the detection area beyond 64 Kbytes by masking bits for match
detection.
Note that during external bus holds, the CS output is set to high impedance.
(1) Register List
15
8
7
0
CAR0
CAR1
CAR2
CAR3
CALR
CMR0
CMR1
CMR2
CMR3
CSCR
R/W
R/W
R/W
R/W
R/W
Chip select area mask register (CMRx)
7
6
5
4
3
2
1
0
0000C0H
0000C2H
0000C4H
0000C6H
M7
M6
M5
M4
M3
M2
M1
M0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
1
R/W
1
R/W
1
R/W
1
Read/write
Initial value
Chip select area register (CARx)
15
A7
14
A6
13
A5
12
A4
11
A3
10
A2
9
8
0000C1H
0000C3H
0000C5H
0000C7H
A1
A0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
Read/write
Initial value
Chip select control register (CSCR)
7
6
5
4
3
2
1
0
0000C8H
⎯
⎯
⎯
⎯
OPL3
OPL2
OPL1
OPL0
Read/write
Initial value
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
R/W
0
R/W
0
R/W
0
R/W
*
Chip select active level register (CALR)
15
14
13
12
11
10
9
8
0000C9H
⎯
⎯
⎯
⎯
ACTL3 ACTL2 ACTL1 ACTL0
Read/write
Initial value
⎯
⎯
⎯
⎯
⎯
⎯
⎯
⎯
R/W
0
R/W
0
R/W
0
R/W
0
* : The initial value of this bit is “1” or “0”.
The value depends on the mode pin (MD2, MD1 and MD0) .
75
FUJITSU [ FUJITSU ]
