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Bus and Memory Control (BCU, MEMC)
Chapter 7
Preliminary User’s Manual U17566EE1V2UM00
7.3.2
Memory controller registers (µPD70F3427 only)
The following registers are part of the Memory Controller. They specify the
type of external device that is connected, the number of data wait states, the
number of address wait states, the number of idle states, and they control
features for page ROM.
(1)
BCTn - Bus cycle configuration registers
The 16-bit BCT0 register specifies the external devices that are connected to
the microcontroller device. The register enables the operation of the Memory
Controller for each chip select signal.
Access
These registers can be read/written in 16-bit units.
Address
BCT0: FFFF F480
H
BCT1: FFFF F482
H
Initial Value
4444
H
Caution
1.
The bits marked with 0 must always be 0.
2.
The bits marked with 1 must always be 1.
3.
To initialize an external memory area after a reset, registers BCTn have to
be set. Do not change this register after initialization. Do not access external
devices before initialization is finished.
I
BCT0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
ME3
1
0
BT30
ME2
1
0
BT20
ME1
1
0
BT10
ME0
1
0
BT00
CS3
CS2
CS1
CS0
BCT1
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
ME7
1
0
BT70
ME6
1
0
BT60
ME5
1
0
BT50
ME4
1
0
BT40
CS7
CS6
CS5
CS4
Table 7-18
BCTn register contents
Bit Position
Bit Name
Function
15, 11, 7, 3
MEk
Enables/disables Memory Controller operation for
chip select area k.
0: Operation disabled
1: Operation enabled
12, 8, 4, 0
BTk0
Specifies the devices that are connected to chip
select area k.
0: SRAM or external I/O connected
1: Page ROM connected
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