廬
APPLICATION BULLETIN
by Miaochen Wu
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ACCESSING THE ADS1210 DEMO BOARD WITH YOUR PC
The ADS1210 demo board along with the PC software is a
complete data acquisition system using the ADS1210 24-bit
delta-sigma analog-to-digital converter. The demo board has
two microcontrollers and 32K on board memory. It is
accessed using a PC program through the PC parallel port.
This application note explains the hardware design and the
software design of the demo board. The hardware design
discusses the system block diagram and the circuit diagram.
The software design discusses the data structure and the core
procedures for the PC programming. An example of PC
Pascal program is provided to illustrate how to access the
ADS1210 demo board. With the understanding of the demo
board design, a new PC program can be implemented to do
the data acquisition using the ADS1210 demo board.
SYSTEM OVERVIEW
The ADS1210 demo board consists of four major devices.
Figure 1 is the system block diagram. The device U4 is
considered as a central control device. It gets instruction
from the PC software, controls the operation of the ADS1210,
and transfers the data converted from the ADS1210 to the
device U5. The device U5 is mainly for the 32K memory
management as U4 is usually heavily loaded by the PC or
the ADS1210. The PC software provided with the ADS1210
demo board is mainly designed for customer to evaluate the
performance of the ADS1210. However, you can write your
own PC program to access the ADS1210 demo board.
PC PORT
PIN NO.
1
2-9
10
11
12
13
14
15
16 - 18
19 - 25
BUS NAME
_STB
DB0 - DB7
DATA3
_BUSY
DATA2
DATA1
AUTOFEED
DATA0
NC
GND
FUNCTION
The PC interrupt signal to the device U4
The PC data or instruction output to the
ADS1210 demo board
The data input from the ADS1210 demo board
The busy signal input from the ADS1210 demo
board
The data input from the ADS1210 demo board
The data input from the ADS1210 demo board
The PC interrupt signal to the device U5
The data input from the ADS1210 demo board
Not connected
Ground
TABLE I. The Pin Connection and the Function of the
Connector J1.
the PC is connected to the demo board by the connector J1.
Table I shows the pin connection and the pin function of the
connector J1.
The PC sends two kinds of information to the ADS1210
demo board. The data is the information that PC sends to or
retrieves from the demo board. The instruction is the infor-
mation that PC sends to the demo board. The demo board
does some operations when an instruction is received.
The PC sends the signal _STB to interrupt the device U4
when the PC wants to access to the device U4. If the device
U4 is busy, the signal _BUSY is sent to the PC to indicate
the busy status of the device.
The PC sends the data or instruction through the data bus
DB0 - DB7, and retrieves the data or instruction through the
data bus DATA3 - DATA0. The data sent by the PC to the
demo board is always in one byte (8-bit) package. However,
the data retrieved by the PC from the demo board is always
in one nibble (4-bit) package.
Figure 3 shows the circuit diagram of the memory manage-
ment section. The PC sends the signal AUTOFEED to
interrupt the device U5 when the PC wants to retrieve the
data from the 32K memory. The data in the 32K memory is
the output data from the ADS1210. The device U5 accesses
the 32K memory with an incremental address. The PC
retrieves data of the 32K memory with a decrement address.
Figure 4 illustrates the memory accessing direction used by
the device U5 and the PC.
The circuit diagram of the ADS1210 device section is not
shown here. Please refer to the ADS1210 demo board data
sheet.
PC
U4
8XC51
Main
Control
U5
8XC51
Memory
Control
U7-U9
32Kx24
Memory
ADS1210/11
DEMO BOARD
FIGURE 1. System Block Diagram.
CIRCUIT DIAGRAM
The ADS1210 demo board circuit diagram consists three
sections: the PC interface section, the memory management
section and the ADS1210 device section. Figure 2 shows the
circuit diagram of PC interface section. The parallel port of
漏
1997 Burr-Brown Corporation
AB-113
Printed in U.S.A. March, 1997
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