VRS1000 데이터 시트보기 (PDF) - Unspecified
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VRS1000 Datasheet PDF : 47 Pages
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VRS1000
VERSA
Datasheet Rev 1.6
Auxiliary P3 Port Functions
The Port3 I/O pins are shared with the UART interface,
INT0 and INT1 interrupts, Timer 0 and Timer 1 inputs
and finally the #WR and #RD lines when external
memory access is performed.
To maintain the correct functionality of the line in
auxiliary function mode, it is necessary that the Q
output of register is held stable at 1. Conversely, if the
pull-down transistor continues conducting, it will set the
IC pin at a voltage of approximately 0.
FIGURE 11: P3 PORT STRUCTURE
Read Regist er
Au xilia ry
Function: Output
Internal Bus
Write to
Regist er
Q
D Flip -Flop
Q
Vcc
X1
IC Pin
Read Pin
Au xilia ry
Function: Input
The following table describes the auxiliary function of
the Port3 I/O pins.
TABLE 17: P3 AUXILIARY FUNCTION TABLE
Pin Mnemonic Function
P3.0 RXD
Serial Port:
Receive data in asynchronous
mode. Input and output data in
synchronous mode.
P3.1 TXD
Serial Port:
Transmit data in asynchronous
mode. Output clock value in
synchronous mode.
P3.2 INT0
External Interrupt 0
Timer 0 Control Input
P3.3 INT1
External Interrupt 1
Timer 1 Control Input
P3.4 T0
Timer 0 Counter Input
P3.5 T1
Timer 1 Counter Input
P3.6 WR
Write signal for external memory
P3.7 RD
Read signal for external memory
Port4
Port4 has four pins and its port address is located at
0D8H.
TABLE 18: PORT 4 (P4) - SFR D8H
7
6
5
4
Unused
3
2
1
0
P4.3 P4.2 P4.1 P4.0
Bit Mnemonic Description
7
Unused
-
6
Unused
-
5
Unused
-
4
Unused
-
3
P4.3
Used to output the setting to pins P4.3,
2
P4.2
P4.2, P4.1, P4.0 respectively.
1
P4.1
0
P4.0
Software Particularities Concerning the Ports
Some instructions allow the user to read the logic state
of the output pin, while others allow the user to read
the content of the associated port register. These
instructions are called read-modify-write instructions. A
list of these instructions may be found in the table
below.
Upon execution of these instructions, the content of the
port register (at least 1 bit) is modified. The other read
instructions take the present state of the input into
account. For example, the instruction ANL P3,#01h
obtains the value in the P3 register; performs the
desired logic operation with the constant 01h; and
recopies the result into the P3 register. When users
want to take the present state of the inputs into
account, they must first read these states and perform
an AND operation between the reading and the
constant.
!
"
When the port is used as an output, the register
contains information on the state of the output pins.
Measuring the state of an output directly on the pin is
inaccurate because the electrical level depends mostly
on the type of charge that is applied to it. The functions
shown below take the value of the register rather than
that of the pin.
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