Real Time Clock USB Evaluation Board V3.0

Transcription

1 Real Time Clock USB Evaluation Board V.0 Application Note February 9, 008 RTC EVB Intersil RTC Devices Supported Introduction This evaluation board provides a platform for testing Intersil Real Time Clock (RTC) devices. Device features include a crystal oscillator, clock and date counters, voltage monitoring and reset, watchdog timer, and alarms. The ISL09/9/ devices include an event-detection and timestamp feature for recording the time of an event. The ISL00/ devices feature a temperature sensor and temperature compensation. The evaluation board provides a platform to test all of these functions, as well as evaluate device performance criteria, such as long-term clock accuracy. Hardware options such as battery and crystal types can also be tested. The software is designed to allow easy setup and monitoring of all major device functions. The two-piece construction utilizing a motherboard and a daughtercard enables the board and software to operate the RTC device residing on a remote board. Operation and Overview of the RTC Evaluation Board Hookup and Power TABLE. With EEPROM No EEPROM No EEPROM ISL04 ISL08 ISL00 ISL05 ISL09 ISL00M ISL06 ISL8 ISL0M ISL07 ISL9 ISL0 ISL08 ISL0 ISL0 ISL09 ISL CONNECTIONS The eval board consists of a motherboard and daughtercard and these need to be connected together. The evaluation board uses a USB connection to communicate and drivers must be installed on each PC that talks to the RTC eval board. A USB cable, with type A and B connectors on the ends, is required to hook up the board to a PC. The cable should be connected to the PC first and then to the eval board. Once connected, the POWER LED will illuminate indicating +5V power is available from the USB cable and the USB has a connection. POWERING DOWN The motherboard contains backup power, consisting of batteries or a supercap. When powering down, the daughtercard will operate off the backup source determined by J4 (after the V CC voltage discharges from the V CC supply capacitors). If the user wishes to totally power down the RTC device once V CC is removed, then either remove the daughtercard from the motherboard or set JP to GND. Keep in mind there is a decoupling capacitor on the daughtercard (0.µF) which must discharge fully before the RTC device stops operating. This discharge time can be up to one second when using a V CC of 5V. Note that when powered down, the RTC board cannot be monitored by the RTC software. Installing the RTC Software and USB Drivers USB SOFTWARE AND DRIVERS SETUP INSTALL BASE SOFTWARE AND DRIVERS Insert CD in the PC. Do not plug in the RTC USB eval board yet. Double click Setup.exe Click to agree on license window, then click to install. AFTER software install, plug the board in and it should bring up the hardware installation wizard window. When asked for the location of drivers, use the CD drive. Click to do the installation of drivers and then finish. The install program will place the RTC evaluation program (RTC.exe) in this location: C:\Program Files\Intersil\RTC Eval INSTALL SOFTWARE UPDATE FOR LATEST DEVICES On the CD, open the folder USB_RTC_Update_V.xx which contains the update executable file. Double click on that file and follow the instructions on the screen. After installation it is a good idea to make a shortcut on your desktop to allow quick startup of the program. Using the Software To start the program, double click on RTC.exe and the opening window should appear as in Figure. This is the Setup screen as indicated on the tab. At the bottom of the window there are status messages for the USB connection. The center message will state if USB is active or inactive, and next to it will be the connect time if the USB RTC board has been plugged in. CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures INTERSIL or Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc All Rights Reserved. All other trademarks mentioned are the property of their respective owners.

2 There are multiple tabs for different setup and RTC functions. The icons at the top will stay visible independent of the tab chosen, as well as the right section displaying polling data. SETUP TAB There are sections to the Setup screen, plus the display section. The left section is for device selection, with a pulldown window to select which Intersil RTC device daughtercard is connected. Details of the selected device features are displayed. Selecting a device here will also set the content of the other tabs to options for that device. Note that the ISL0 selection ALSO supports the ISL0M and ISL00M modules. The middle section has 5 functions. Vcc enabled is the status of the Vcc switch on the motherboard. Clicking the window here will enable or disable Vcc to the daughtercard. The switch icon in the top icon bar will do the same. The I C buss speed can be selected, either 00kHz or 400kHz. The temp sensor type can be selected (RTC daughtercards have either LM75 or LM76) and the sensor temperature output can be calibrated, the offset selected in that window is reflected in the temp sensor output display on the right. The Eval Board Select function can select among multiple Intersil eval boards connected to a PC, and should be set to usb_rtc. PC time format controls how the PC time window displays time, either or 4 hour (military) format. The right section is the status display and clear section. The relevant status bits for the device are displayed as lights in the upper section, and those bits can be cleared using the buttons in the lower section. FIGURE. EVALUATION SOFTWARE GUI MAIN TAB The display section appears regardless of tab selected and contains the following windows: PC Time - The time kept on the PC, displayed all the time RTC Time - the monitored RTC device time, displayed while Polling is enabled RTC Deviation - the delta between RTC device time and PC time PC date - the current date kept on the PC, displayed all the time RTC date - the monitored RTC date, displayed while polling is enabled. Temperature - the current reading of the temperature sensor, displayed while polling is enabled. If there is no temperature sensor the window will be blank. The Intersil RTC device daughtercards use the LM75 device. Older daughtercards may have used the LM76 device. The temperature section allows selection of either device. SET CLOCK TAB This tab contains sections, Time and Data, Adjust RTC from PC Clock, and Adjust RTC from Time and Date Selection. The display section on the far right should have polling enabled in order to check the RTC time and date when doing Set Clock functions. Time and Data Selection - allows selection of the time/date that can be written to the RTC device. Includes /4 hour format selection. Adjust RTC from PC Clock - two options. Write to the RTC device the current PC time/date, or write to the PC clock with the current RTC time/date. Note that if the latter is chosen, the current PC time and date will be lost. Adjust RTC from Time and Data - two options. Set RTC Date and Time will take the date and time from the Time RTC EVB February 9, 008

3 and Data selection window on the left and write to the RTC device. Second selection is to write the current RTC time to the Data Selection window. REGISTERS TAB This tab enables reading and writing to each of the registers in the RTC device. The pulldown window at top will allow selection of one of the list of the different register groups (the groups will correspond to those of the device chosen in the Setup Tab). For writing, it is possible to change individual bits using the cells in each register, or to change the hex value in the column on the left. After changing the register value, the Write button for the register must be clicked under the Byte Operation column, or the page write at the bottom can be used. For reading, the individual registers can be read or the page read at the bottom can be used. Note that performing operations in the other tabs will change the registers in a device, and those results can be read directly in the Registers tab. Also, changes made in the Registers tab will be reflected in the tabs for the corresponding functions. GRAPH TAB The program is able to record continuous time measurements of the RTC deviation from PC Clock and the board temperature and create a plot of the results. Time frames from a few minutes to many days are possible. First select the deviation range in pulldown window in the lower right corner for the time scale. The Temperature Range and Time Base (measurement time length) should also be set as desired from their pulldown windows. Set the RTC time from the PC time as described above. This will insure the PC time is close to the RTC time to begin recording. To begin recording, check the Enable Polling box in the Data display on the right. The graph will automatically record data as long as the polling function is enabled. Graphing will stop when polling is disabled and will start again where the data left off when enabled again. If you wish to collect new data, then click the Restart button. the PC time, such as that available from NIST INTERRUPT TAB This tab contains control for the Frequency Output pin. The pulldown window allows selection of frequency for the device chosen. There is also a check box for frequency output in battery backup mode. To correctly perform a write, the data must be selected, then the write button is selected. To read, just select the read button. ALARM TAB The left side of the window contains the controls to enable the alarm and alarm mode, as well as pulldowns to select the alarm time/date match conditions. Note that the hours pulldown contains entries for both Military and regular time, and this must correspond to the time display chosen for the RTC registers. To correctly perform a write, the data must be selected, then the write button is selected. To read, just select the read button. The right side window contains the status for the alarm. EVENT TAB (ISL09, 9, ONLY) This tab controls all the Event and Timestamp functions, when available. The left side of the window contains the control register bits to enable the event detection and set the timing and hysteresis functions. Controls for the event detect in battery mode, halt RTC on event, and the current source disable are included. To correctly perform a write, the data must be selected, then the write button is selected. To read, just select the read button. The right side of the window includes the status indicator, and also a window to show the timestamp register, if available (not on ISL09). CRYSTAL COMP TAB This tab includes control checkboxes for the bits of control for the RTC compensation features. ATR, DTR, and Battery Mode ATR controls are included. To correctly perform a write, the data must be selected, then the write button is selected. To read, just select the read button. Data will be recorded periodically until the end of the time frame selected or until polling is stopped. Note that multiple samples are recorded and averaged before being plotted on the chart recorder. The raw data can be saved to a file for other uses such as in a spreadsheet. Choose a file folder using the folder icon in the menu bar. Then use the save file icon to choose a file name and save. The start time is shown at the bottom left of the screen for reference. Note that for long recordings of deviation, it is advisable to use a PC program that automatically updates RTC EVB February 9, 008

4 Hardware and Software Detailed Descriptions USB RTC Evaluation Board - General Description The evaluation board consists of the motherboard and daughtercard. The motherboard contains all the main support functions for the RTC device, including: Microcontroller with USB interface for communicating with the PC and the RTC. I C Buffer IC for allowing variable IC pullup voltages 5V board supply from the USB, and a regulated.v supply. Connectors for the USB interface and the daughtercard. A 00uF supercapacitor, a.v rechargeable lithium battery, and a socket for a CR0 V lithium coincell battery for backup power. Jumpers for selecting which backup battery or supercapacitor, and also for selecting the V CC voltage of 5V or.v. A MOSFET switch controlled by the microcontroller which disconnects the V CC supply from the daughtercard for backup testing. Testpoints for monitoring the SCL and SDA lines plus ground. The daughtercard contains the Intersil RTC device, crystal, temperature sensor IC, decoupling capacitor, and pullup resistor for the open drain output. Daughtercards with event detect IC s also contain an event detect switch plus jumper for selecting the event input connection. For individual daughtercard schematics, contact Intersil. DAUGHTERCARD ON/OFF CONTROL The normally open switch icon in the menu bar controls whether V CC power is applied to the daughtercard. Click on the icon once to shut off V CC power and the icon will show the open switch. Click again on the icon to reapply V CC power and the icon will close the switch. Note that when V CC power is turned off, the RTC device will operate from backup power selected by J4 on the motherboard. No communication with the device is possible in backup mode. Evaluation Board - Functional Description (see Figure and Schematic) POWER SUPPLY The motherboard draws its power from the USB +5V ±5% supply. If the eval board is used to provide power for other circuitry, care must be taken to keep the current draw on this supply well below 500mA which is the maximum for a USB hub-type device. There is an on-chip regulator which produces.v at low output current (<0mA). The V CC for the Intersil RTC chip as well as the serial interface pullup resistors is selectable using J for either.v or 5V. If an external V CC supply is used it should be connected to the center pin of JP (shunt is removed). A ground test point is available as well. BACKUP SUPPLY There are two sources of backup supply available. A 00µF supercapacitor (C0) is on the board. It will provide enough backup power for the typical RTC chip to last about minute at room temperature when V CC is set to 5V. There is also a CR0 battery socket to allow removal/ replacement without soldering. This battery will last up to five years in normal backup operation. The backup supply is selectable via jumper J4 as shown in Figure. One row of J4 is connected to the device V BACK, and the other row to the power sources. There are four positions possible on J4, Supercap, Rechargeable, CR0 Battery, and Ground. If no backup is used the Ground position should be used. The jumper may be removed altogether and an alternative source for V BACK can be attached to the board via the exposed header. MICROCONTROLLER The microcontroller used is the C805F0. There is a dedicated I C serial interface connected to the Intersil RTC device, EEPROM, and the temperature sensor. The power for the microcontroller comes from the USB 5V input, so the microcontroller will always be powered from 5V. Note that the P.0 to P.4 I/O pins for the microcontroller are available at the daughtercard connector, J. These are for future functions and should not be loaded down or used otherwise. J is a microcontroller programming connector and should not be used. DAUGHTERCARD CONNECTOR (J) This connector provides power and interface signals to the daughtercard containing the Intersil RTC device as shown on the board silkscreen. This configuration allows these signals to control the Intersil device on an external board by connecting the serial interface and ground, available at the connector. Also available are the P.0 to P.4 I/O signals from the microcontroller (see previous section). USB CONNECTOR (CON) This connector is a standard USB type B connector which goes to the USB port of a PC using a USB type A-B cable. LEDs There one surface-mounted LED on the board. It is labeled POWER and it monitors the power supply and will light when the +5V power is applied from the USB cable. when the PC is communicating with the Eval board, the light will blink. Daughtercards - Functional Description 4 RTC EVB February 9, 008

5 The Daughtercards have a 0-pin female connector which matches with the Motherboard connector. There are multiple header connections on each daughtercard, the only jumper which is required to be connected with a shunt is the Device Vcc header, which connects Vcc power to the RTC device. This allows the current to the RTC device to be monitored when removed. Other headers for output signals may be removed. There is a temperature sensor on the board as well which can be used for monitoring temperature in the case of crystal frequency drift testing. The PC software can poll the temp sensor while polling the RTC time. The devices that include event detection (ISL09/9/) will also have an event detect switch on the daughtercard. There is a header with an option to turn off the internal current source and use an external pullup to Vcc or Vbat. INDICATOR LEDS JP4 and JP5 connect LEDs for the Event and IRQfunctions, respectively. Remove these jumpers if no indicator is desired for these functions. D and D4 are indicator LEDs for the AC Ready and Low Voltage detect functions, respectively. They do not have jumpers and are active at all times. OTHER FUNCTIONS The Fout function is at JP8-. There is a ground connection at JP8- for connecting an instrument (such as a frequency counter) with a ground lead. JP is the DEVICE Vcc jumper. If Device Icc current measurement is desired, remove this jumper to insert an ammeter in the circuit THE ISL0 DAUGHTERCARD The ISL0 device possesses many more features than the other Intersil RTC devices so the evaluation daughtercard is a bit more complex. The schematic is shown in Figure and the layout is in Figure 4. AC INPUT The ISL0 can use an external 50Hz or 60Hz AC power clock for the internal time clock. There are two ways to hook this up. One way is to use a transformer with a sine wave output, connected to JP (TFR). This input is conditioned by a selectable voltage divider and AC coupled to an emitter follower, which assures the peak voltages are never more than the Vdd/GND of the RTC device. The ratios for the resistor divider are as follows: R: 0.0 x V TRF R: 0.8 x V TRF R: 0. x V TRF The TFR input has no polarity, connections can be reversed as long as the transformer output used is not grounded. If the TFR input is used, then a jumper MUST be placed across JP, ACIN, so that the clock signal reaches the RTC device. If a single ended sine wave or square wave clock source is used (such as from a waveform generator), it should be connected to the ACIN jack at JP-, and the signal ground should connect to a nearby ground. The amplitude should be from.5vpp to 4Vpp. EVENT FUNCTION S is the Event Switch for the ISL0, and jumper JP7 must be installed to connect the switch leads to ground. Jumper JP8 can be used to select an external pullup resistor, with either device Vcc or Battery pullup voltage. Remove JP8 if the internal pullup is used. 5 RTC EVB February 9, 008

6 . V CC SELECT DAUGHTERBOARD CONNECTOR USB CONNECTOR SUPERCAP BACKUP BATTERY SOCKET SHUNT FOR V BACK SELECT FIGURE. RTC EVB Motherboard Layout 6 RTC EVB February 9, 008

7 4 6 5 Application Note RTC EVB FIGURE. ISL0 DAUGHTERCARD SCHEMATIC JP AC IN D JP TFR R4 75K R5 K JP9 R 0K R 0K R 80 C4 uf R6 4K R0 68K Q MMBT904 R8 0k C 0 uf C5 uf JP DEVICE VCC TP4 ACR ACRDY C 0.0uF D LTST-C0KRKT R9.K D C J EVDETOUT SDA SCL VBAT Y.76 khz U X VCC X IRQ VBAT SCL GND SDA AC ACRDY LV FOUT EVIN EVDET ISL R D.K IRQ LTST-C0KRKT R D.K EVDETOUT LTST-C0KGKT FOUT JP4 JP5 JP6 IRQ- Jumper EVDET Detect Jumper FOUT Jumper C B SDA SCL U SDA +VS SCL A0 TCA A 4 GND INT LM75 D4 R5.K LTST-C0KRKT C 0.uF LV TP5 LV VCC_DEV EVIN R4 VBAT S EVIN Detect Switch JP8 5M JP7 EVIN Pullup B A GND GND GND Title ISL0 TSSOP EVAL DAUGHTERCARD A A FIGURE 4. ISL0 DAUGHTERCARD LAYOUT Size: Revision: 7 RTC EVB February 9, 008

8 Appendix A: RTC Motherboard Schematic Application Note RTC EVB 8 RTC EVB February 9, 008