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8-5
power-on memory mapping configurations, the
SYM53C040 address decode logic will automatically
provide the first branch instruction to the microcontroller
whenever it fetches from address 0x0000 through
0x0002. The values in bits 0 and 1 define the destination
address for this branch instruction, according to
. For more information on automatic branch
addressing, see
The reset value of these bits matches the TTL voltage
levels on the AD0 and AD1 pins on reset. These pins
have internal pull-down resistors, so if no external pull-up
resistor is used, the reset value is 0, and the first
microcontroller instruction will be fetched from address
0x0000. If an external pull-up resistor is used, the reset
value is 1.
Register: 0xFF03
Power-On Configuration One (POC1)
Read Only
This register is not affected by a soft reset.
R
Reserved
7
This bit should remain clear (0) for normal operation.
POC1_6
Power-On Configuration 1_6
6
The reset value of this bit matches the TTL voltage level
on the A14 pin on reset.
Table 8.2
Automatic Branch Destination Address
FIBD1
FIBD0
Branch Destination
1
1
0x8000
1
0
0x4000
0
1
0x0033
0
0
Fetched from 0x0000
7
6
5
4
3
2
1
0
R
POC1_6
POC1_5
POC1_4
DLSEL
DLADR2
DLADR1
DLADR0
Defaults:
A15
A14
A13
A12
A11
A10
A9
A8
Содержание Symbios SYM53C040
Страница 12: ...xii Preface...
Страница 90: ...4 18 SCSI and DMA Registers...
Страница 98: ...5 8 SFF 8067 Registers...
Страница 110: ...6 12 Two Wire Serial Registers...
Страница 126: ...7 16 Miscellaneous Registers...
Страница 160: ...8 34 System Registers...
Страница 184: ...9 24 Electrical Characteristics...
Страница 194: ...A 10 Register Summary...
Страница 214: ......