MB90480/485 Series
18. External Bus Pin Control Circuit
The external bus pin control circuit controls the external bus pins used to expand the CPU address/data bus
connections to external circuits.
(1) Register List
• Auto ready function select register (ARSR)
Initial value
15
14
13
12
11
10
9
8
Address : 0000A5H
0011--00B
IOR1
IOR0
HMR1
HMR0
⎯
⎯
LMR1
LMR0
W
W
W
W
⎯
⎯
W
W
• External address output control register (HACR)
Initial value
********B
7
6
5
4
3
2
1
E17
0
E16
Address : 0000A6H
E23
E22
E21
E20
E19
W
E18
W
W
W
W
W
W
W
• Bus control signal select register (EPCR)
Initial value
1000*10-B
15
14
13
12
11
10
9
8
Address : 0000A7H
CKE
RYE
HDE
IOBS
W
HMBS
W
WRE
W
LMBS
W
⎯
W
W
W
⎯
W
−
*
: Write only
: Not used
: May be either “1” or “0”
(2) Block Diagram
P5
P4
P3
P5
P2
P1
P0
P0
P0 data
P0 direction
RB
Data control
Address control
Access control
Access control
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