73M2910L Просмотр технического описания (PDF) - TDK Corporation
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73M2910L Datasheet PDF : 35 Pages
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73M2910L
Microcontroller
USR3 PORT (continued)
USR3 I/O Port Direction (DIR3) External Address 0001h
Byte Addressable
Reset State FFh
BIT 7
DIR3.7
BIT 6
DIR3.6
BIT 5
DIR3.5
BIT 4
DIR3.4
BIT 3
DIR3.3
BIT 2
DIR3.2
BIT 1
DIR3.1
BIT 0
DIR3.0
This register is used to designate the USR3 pins as either inputs or outputs. If the register bit is reset to a 0, the
corresponding USR3 pin is programmed as an output that will be driven by the corresponding USR3 data
register bit. If the register bit is a 1, the corresponding pin will be treated as an input.
After a reset, the USR3 pins will present a high impedance output state and the input values will not be driven
from the pin, but will be driven to a 1 internally. The pins will assume normal I/O operation once the processor
has written the USR3 port direction register. This feature will ensure a low current state at reset.
If the bank select feature is chosen, USR3.7 pin is forced to be an output.
BANK SELECT (BNKSEL) EXTERNAL ADDRESS 0002h
Byte Addressable
Reset State 00h
BIT 7
B7
BIT 6
B6
BIT 5
B5
BIT 4
B4
BIT 3
B3
BIT 2
BSEN
BIT 1
BS1
BIT 0
BS0
This register is used to accommodate systems where more than 64 kBytes (up to 128 kBytes) of program
memory are required. Pin USR3.7 acts as an address pin, A16, if BSEN is set to a 1 and the processor is
fetching an instruction and not data memory. If BSEN is set to a 1, A15 is also modified during instruction
fetches as shown below. If BSEN is a 0, no alterations to address bit A15 are made, and pin USR3.7 is a
function of USR3 bit 7 and DIR3 bit 7.
Bits (7:3) are general purpose read/write register bits.
A15
A15’
A16
Value of the 16th address bit as it appears at pin A15.
Address from port 2 internal logic, the value that will appear as the most significant address bit if no
bank select feature is chosen.
Value of the 17th and MSB of the instruction address seen at the USR3.7 port pin, if the bank select
feature is selected. If the bank select feature is not selected, USR3.7 acts as a normal USR3 I/O port
pin.
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