LM12434CIWM NSC [National Semiconductor], LM12434CIWM Datasheet - Page 41

• Manufacturer Part Number: LM12434CIWM
• Description: Sign Data Acquisition System with Serial I/O and Self-Calibration
• Manufacturer: NSC [National Semiconductor]

7 0 Digital Interface
In order to read from or write to the registers of the
LM12434 and LM12 L 438 a very flexible serial synchro-
nous interface is provided Communication between the
LM12434 and LM12 L 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
ditional hardware required The interface has been also de-
signed to accommodate easy and straightforward software
programming
The LM12434 and LM12 L 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 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
Interface
Standard
8051
TMS320
I
Internally pulled-up
2
C
Mode
M0DESEL1
0
0
1
1
TABLE VI LM12434 and LM12 L 438 Interface Modes and Pin Assignments
2
C serial protocol with no ad-
MODESEL2
1
0
1
0
Slave AD0
FSR
R F
P1
1
41
The ‘‘I
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
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
can be connected to an I
(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 L 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 L 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 L 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 L 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
If R F
and captured at the rising edge of the SCLK
If R F
and captured at the falling edge of the SCLK
Slave AD1
2
C’’ mode supports the Philips’ I
FSX
CS
P2
e
e
1
1 data is shifted after falling edge and is stable
0 data is shifted after rising edge and is stable
Slave AD2
2
P3
CS
DX
DI
C bus using an I
2
2
2
C bus specification
C bus and receives
C Interface mode
RXD
SDA
DO
DR
P4
2
C controller
SCLK
TXD
CLK
SCL
P5