6.1.3 Input/Output Pins
Table 6-1 summarizes the bus controller’s input/output pins.
Table 6-1 Bus Controller Pins
Name
Abbreviation
I/O
Function
Chip select 0 to 7
CS
0
to CS
7
Output
Strobe signals selecting areas 0 to 7
Address strobe
AS
Output
Strobe signal indicating valid address output on the
address bus
Read
RD
Output
Strobe signal indicating reading from the external
address space
High write
HWR
Output
Strobe signal indicating writing to the external
address space, with valid data on the upper data
bus (D
15
to D
8
)
Low write
LWR
Output
Strobe signal indicating writing to the external
address space, with valid data on the lower data
bus (D
7
to D
0
)
Wait
WAIT
Input
Wait request signal for access to external three-
state-access areas
Bus request
BREQ
Input
Request signal for releasing the bus to an external
device
Bus acknowledge
BACK
Output
Acknowledge signal indicating the bus is released
to an external device
6.1.4 Register Configuration
Table 6-2 summarizes the bus controller’s registers.
Table 6-2 Bus Controller Registers
Initial Value
Address
*
Name
R/W
Modes 1, 3, 5, 6
Modes 2, 4, 7
H'FFEC
Bus width control register
ABWCR
R/W
H'FF
H'00
H'FFED
Access state control register
ASTCR
R/W
H'FF
H'FF
H'FFEE
Wait control register
WCR
R/W
H'F3
H'F3
H'FFEF
Wait state controller enable
WCER
R/W
H'FF
H'FF
register
H'FFF3
Bus release control register
BRCR
R/W
H'FE
H'FE
H'FF5F
Chip select control register
CSCR
R/W
H'0F
H'0F
Note:
*
Lower 16 bits of the address.
Abbrevi-
ation
113
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