19-1874; Rev 0; 12/01
MAX1756 Evaluation System
EV System Component List
PART
QTY
MAX1756EVKIT
1
MAX1756 evaluation kit
DESCRIPTION
MAXSMBUS
1
PC parallel port to SMBus
interface
EV Kit Component List
REFERENCE
QTY
C1
1
DESCRIPTION
0.1µF 0805 ceramic capacitor
U1
1
MAX1756AAUT
JU1
1
3-pin jumper
H1
1
6-pin header
P1
1
2 × 10 female right-angle
receptacle
None
1
PC board
None
1
MAX1756 data sheet
None
1
MAXSMBUS manual (included
in MAX1756EVKIT manual)
None
1
3-1/2in software diskette,
MAX1756EVKIT
MAX1756 EV Kit Files
INSTALL.EXE
Installs the EV kit files on your computer
MAX1756.EXE
Application program
LPTCON.VXD
Required parallel port driver
Features
♦ Proven PC Board Layout
♦ Convenient On-Board Test Points
♦ Fully Assembled and Tested
Ordering Information
PART
TEMP RANGE
INTERFACE TYPE
MAX1756EVSYS
0°C to +70°C
Windows software
MAX1756EVKIT
0°C to +70°C
User-supplied
Recommended Equipment
Before you begin, you will need the following equipment:
• Maxim MAX1756EVKIT and MAXSMBUS interface
board
• 12VDC power supply
• Computer running Windows 95/98
• Spare parallel port
• 25-pin I/O extension cable
Quick Start
1) With the power off, connect the 12VDC power supply to the MAXSMBUS board between POS9 and
GND. The MAX1756 IC’s 5V supply comes from the
MAXSMBUS board.
2) Connect the boards together.
3) Connect the 25-pin I/O extension cable from the
computer’s parallel port to the MAXSMBUS board.
The software uses a loopback connection to confirm
that the correct port has been selected.
4) Ensure that the jumper settings are in the default
position (Table 1).
5) Install the software on your computer by running the
INSTALL.EXE program on the floppy disk. The program files are copied and icons are created for
them in the Windows start menu.
6) Turn on the power supply.
7) Start the MAX1756 program by opening its icon in
the start menu.
8) Click on the Measure Temperature (SAR) button,
and observe the measured temperature.
SMBus is a trademark of Intel Corp.
Windows 95/98 is a registered trademark of Microsoft Corp.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
Evaluates: MAX1756
General Description
The MAX1756 evaluation system (EV system) consists
of a MAX1776 evaluation kit (EV kit) and a companion
Maxim system management bus (SMBus) interface
board.
The MAX1756 EV kit is an assembled and tested circuit
board that demonstrates the MAX1756 SOT23 local
temperature comparators with SMBus serial interface.
Windows® 95/98 software provides a handy user interface to exercise the MAX1756’s features.
Order the MAX1756EVSYS for complete PC-based evaluation of the MAX1756. Order the MAX1756EVKIT if you
already have an SMBus interface.
Evaluates: MAX1756
MAX1756 Evaluation System
Reading the Status
Table 1. Jumper Functions
JUMPER
POSITION
FUNCTION
JU1
1-2*
ADD pin connects to VDD
JU1
open
JU1
2-3
ADD pin is floating
ADD pin connects to GND
*Default configuration
Detailed Description
of Software
Selecting the Device Address
The device address drop-down combo box determines
the SMBus address of the device under test. If the
question mark (?) is selected, then the software automatically tries each possible address until it finds a
device. Each of the supported devices has three possible addresses, depending on the state of the ADD pin.
Refer to the MAX1756 data sheet.
Writing the Command
Clicking the Write command button sends the selected
command to the device under test. The most significant
bit is used to mask under-threshold interrupts or to
make the output pin active-high, depending on which
type of device is being used. The shutdown checkbox
sets the temperature threshold code to -128, placing
the device in standby mode. Codes between -28 and
-127 correspond to a temperature threshold of -54°C
(refer to the MAX1756 data sheet). Changes to the controls are effective immediately if the Auto Write box is
checked.
2
The status byte is read periodically if the Auto Read
box is checked. Otherwise, the status bytes are read by
clicking the Read Status button. Some of the bit definitions are device dependent.
Measuring Temperature
Clicking the Measure Temperature button makes the
PC software determine the temperature by successive
approximation. The high and low brackets of the
unknown temperature range are displayed as THI and
TLO, and each test iteration selects a trial temperature
halfway between THI and TLO. After a programmable
delay time, the status byte is read and the trial value is
copied into THI or TLO, depending on the OVER status
bit. After eight trials, the 8-bit temperature code is completely determined. The EV kit software performs the
equivalent to the algorithm in Listing 1, with some additional user interface code.
Detailed Description
of Hardware
Troubleshooting
Problem: Cannot find MAX1756 parallel port connection.
Ensure that the I/O extension cable is connected to a
parallel port, and not an SCSI or other type of port. Verify
that the supplied LPTCON.VXD is in the same directory
as MAX1756.EXE. If a local printer driver is installed,
temporarily disable it. The software will not work if the
program icon is dragged onto the Windows desktop;
instead, install the software into a subdirectory, such as
C:\MAX1756. The software can also be run directly from
its floppy disk, as long as both MAX1756.EXE and
LPTCON.VXD are in the same directory.
_______________________________________________________________________________________
MAX1756 Evaluation System
Evaluates: MAX1756
Listing 1. Measuring Temperature by Successive Approximation
/* Use successive approximation to measure the ambient temperature.
** Returns the measured temperature in degrees C.
**
** global variables:
** __int8 shadow_command contains the last command we wrote
** __int8 shadow_status contains the last status value we read
**
** External functions:
** SMBusSendByte(__int8 address, __int8 command);
** SMBusReceiveByte(__int8 address, __int8* received_data);
** Delay_msec(int delay_time_msec);
*/
int MeasureTemperature()
{
/* Write a test temperature, then read the status byte.
** Use the state of the OVER bit to determine each successive bit.
*/
signed __int8 Thi = 127;
/* upper limit starts at maximum */
signed __int8 Tlo = -128;
/* lower limit starts at minimum */
while ( (Thi - Tlo) > 0 ) {
signed __int8 Ttest = (Thi + Tlo) / 2;
SMBusSendByte(address, Ttest);
shadow_command = Ttest;
Delay_msec(SAR_delay_time);
/* guess between Thi and Tlo */
/* set new threshold */
SMBusReceiveByte(address, &shadow_status);
/*
if (shadow_status & 0x80) {
/*
if (Tlo == Ttest)
break;
/* close enough, exit loop */
Tlo = Ttest;
} else {
/*
if (Thi == Ttest)
break; /* close enough, exit loop */
Thi = Ttest;
}
}
return Ttest*2;
get status byte */
over temperature? */
/* move lower limit up */
not over temperature */
/* move upper limit down */
/* temperature in degrees C = twice the threshold number */
}
_______________________________________________________________________________________
3
Evaluates: MAX1756
MAX1756 Evaluation System
VCC
P1-5
1
H1-3
P1-2
3
JU1
1
2
U1
GND
6
H1-2
VCC
P1-4
P1-6
H1-4
P1-8
P1-10
ADD
2
MAX1756
SMBDATA
VCC
5
P1-3
P1-9
P1-12
H1-5
H1-1
C1
0.1µF
3
SMBCLK
ALERT
4
P1-7
P1-14
P1-13
P1-16
P1-15
P1-18
P1-17
P1-19
P1-20
Figure 1. MAX1756 EV Kit Schematic
4
_______________________________________________________________________________________
P1-1
H1-6
P1-11
MAX1756 Evaluation System
Evaluates: MAX1756
1.0"
1.0"
Figure 2. MAX1756 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX1756 EV Kit PC Board Layout—Component Side
_______________________________________________________________________________________
5
Evaluates: MAX1756
MAX1756 Evaluation System
1.0"
Figure 4. MAX1756 EV Kit PC Board Layout—Solder Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.