參數(shù)資料
型號(hào)： LM12434
廠商： National Semiconductor Corporation
英文描述： Sign Data Acquisition System with Serial I/O and Self-Calibration
中文描述： 注冊(cè)數(shù)據(jù)采集系統(tǒng)的串行I / O和自校準(zhǔn)
文件頁(yè)數(shù)： 41/80頁(yè)
文件大?。?/td> 1561K
代理商： LM12434
7.0 Digital Interface
In order to read from or write to the registers of the
LM12434 and LM12
à
L
ó
438 a very flexible serial synchro-
nous interface is provided. Communication between the
LM12434 and LM12
à
L
ó
438 and microcontrollers, micro-
processors and other circuitry is accomplished through this
serial interface. The serial interface is designed to directly
communicate with synchronous serial interface of the most
popular microprocessors and I
2
C serial protocol with no ad-
ditional hardware required. The interface has been also de-
signed to accommodate easy and straightforward software
programming.
The LM12434 and LM12
à
L
ó
438 supports four selectable
protocols as shown in Table VI. The MODESEL1 and
MODESEL2 inputs select the desired protocol. These pins
are normally hardwired for a selected protocol, but they can
also be controlled by the system in case a protocol change
within the system is required. P1–P5 are multi-function seri-
al interface input or output pins that have different assign-
ments depending on the selected interface mode.
The ‘‘Standard’’ interface mode uses a simple shift register
type of serial data transfer. It supports several microcontrol-
lers’ serial synchronous protocols, including: National Semi-
conductor’s MICROWIRE/PLUS, Motorola’s SPl, QSPl, and
Hitachi’s synchronous SCl. Section 7.1.1 shows general
block diagrams of how the serial DAS, configured in the
Standard Interface Mode, can be connected to the HPC and
68HC11. Also, detailed assembly routines are included for
single writes, single reads and burst read operations.
The ‘‘8051’’ mode supports the synchronous serial interface
of the 8051 family of microcontrollers (8051 serial interface
Mode 0). It is also compatible with the serial interface in the
MCS-96 family of 16-bit microcontrollers. Section 7.2.1
shows a general block diagram of how the serial DAS, con-
figured in the 8051 Interface Modes can be connected to
the 8051 family of
m
Cs. Also, detailed assembly routines for
a single write, single read and burst read operations are
included.
The ‘‘TMS320’’ mode is designed to directly interact with
the serial interface of the TMS320C3x and TMS320C5x
families of digital signal processors. This interface is also
compatible with the similar serial interfaces on the
DSP56000 and the ADSP2100 families of DSP processors.
Section 7.3.1 shows a general block diagram of how the
serial DAS, configured in the TMS320 interface mode, can
be connected to the TMS320C3x family of DSP processors.
Also, detailed assembly routines for a single write, single
read and burst read operations are included.
The ‘‘I
2
C’’ mode supports the Philips’ I
2
C bus specification
for both the standard (100 kHz maximum data rate) and the
fast (400 kHz maximum data rate) modes of operation. The
DAS behaves as a slave device on the I
2
C bus and receives
and transmits the information under the control of a bus
master. Section 7.4.1 shows a general block diagram of
how the serial DAS, configured in the I
2
C Interface mode,
can be connected to an I
2
C bus using an I
2
C controller
(PCD8584).
All the serial interface modes allow for three basic types of
data transfer; these are single write, single read and burst
read. In a single write or read, 16 bits (2 bytes) of data is
written to or read from one of the registers inside the DAS.
In a burst read, multiple reads are performed from one regis-
ter without having to repeatedly send the control and regis-
ter address information for each read. The burst read can
be performed on any LM12434 and LM12
à
L
ó
438’s register,
however it is primarily provided for multiple reads from the
FlFO register (one address, 32 locations), where a se-
quence of conversion results is stored.
7.1 STANDARD INTERFACE MODE
The standard interface mode is a simple shift register type
of serial data transfer. The serial clock synchronizes the
transfer of data to and from the LM12434 and LM12
à
L
ó
438.
The interface uses 4 lines: 2 data lines (DI and DO), a serial
clock line (SCLK) and a chip-select (CS) line. More than one
device can share the data and serial clock lines provided
that each device has its own chip-select line.
The LM12434 and LM12
à
L
ó
438 standard mode is selected
when the MODESEL1 and MODESEL2 pins have the logic
state of ‘‘01’’.Figure 12 shows a typical connection diagram
for the LM12434 and LM12
à
L
ó
438 standard mode serial
interface. The CS, DI, DO, and SCLK lines are respectively
assigned to interface pins P2 through P5. The P1 pin is
assigned to a signal called R/F (Rise/Fall). The logic level
on this pin specifies the polarity of the serial clock:
D If R/F
e
1, data is shifted after falling edge and is stable
and captured at the rising edge of the SCLK.
D If R/F
e
0, data is shifted after rising edge and is stable
and captured at the falling edge of the SCLK.
TABLE VI. LM12434 and LM12
à
L
ó
438 Interface Modes and Pin Assignments
Interface
Mode
M0DESEL1
MODESEL2
P1
P2
P3
P4
P5
Standard
0
1
R/F
CS
DI
DO
SCLK
8051
0
0
1
*
1
*
CS
RXD
TXD
TMS320
1
1
FSR
FSX
DX
DR
CLK
I
2
C
1
0
Slave AD0
Slave AD1
Slave AD2
SDA
SCL
*
Internally pulled-up
41
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