DS2480B Maxim Integrated Products, DS2480B Datasheet
DS2480B
Specifications of DS2480B
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DS2480B Summary of contents
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... DESCRIPTION The DS2480B is a serial port to 1-Wire interface chip that supports regular and overdrive speeds. It con- nects directly to UARTs and 5V RS232 systems. Interfacing to RS232C (±12V levels) requires a passive clamping circuit and one 5V to ±12V level translator. Internal timers relieve the host of the burden of generating the time-critical 1-Wire communication waveforms ...
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... DS2480B can translate each character into eight 1-Wire time slots, thereby increasing the data throughput significantly. In addition, the DS2480B can be set to communicate at four different data rates, including 115.2kbps, 57.6kbps, and 19.2kbps, with 9.6kbps being the power-on default. Command codes received from the host’ ...
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... Post-calibration changes cause calibration error to exceed ±5%. The DS2480B requires a 1-Wire reset command sent by the host at a data rate of 9600bps for calibration. Data rates of 115200bps or higher during calibration may put the DS2480 in an undefined state, requiring a power-down reset to restore normal operation. ...
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Figure 2. STATE TRANSITION DIAGRAM LEGEND: V BINARY VALUE (TYPE OF WRITE TIME SLOT) SS 1-WIRE SPEED SELECTION CODE P IF LOGIC 1, GENERATES STRONG PULLUP TO 5V IMMEDIATELY TIME SLOT T TYPE OF PULSE STRONG PULLUP (5V), ...
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... XXXXXX01b. The Xs represent undefined bit values. The fact that the host receives the byte unsolicited together with the pattern 01b in the least significant 2 bits marks the bus arrival. If the DS2480B is left in Data Mode after completing a memory function command it will not report any bus arrival to the host. ...
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... Read Data time slot is identical to the Write-1 time slot. Bits 0 and 1 of the response byte transmitted by the DS2480B at the end of the time slot reveal the value found on the 1-Wire bus when reading. For a time slot without a subsequent strong pullup, bit 1 of the command must be set to 0. For a time slot immediately followed by a strong pullup bit 1 must be set to 1 ...
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Table 1. COMMUNICATION COMMAND CODES FUNCTION BIT 7 BIT 6 Single Bit 1 Search Accelerator 1 Control Reset 1 Pulse 1 Table 2. COMMUNICATION COMMAND RESPONSE FUNCTION BIT 7 BIT 6 Single Bit 1 0 Reset 1 1 Pulse 1 ...
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... Configuration Commands section). However, unlimited duration is not allowed in conjunction with arming the strong pullup after every byte. As long as the DS2480B is in Command Mode the host may terminate a strong pullup or programming pulse prematurely at any time by sending the command code F1h ...
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... The character “r” marks the path that particular bit in case of a conflict during the execution of the ROM Search. For each bit position n (values from 0 to 63) the DS2480B will generate three time slots on the 1-Wire bus. These are referenced as: ...
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... The type of time slot b2 (write 1 or write 0) is determined by the DS2480B as follows conflict (as chosen by the host conflict (there is no alternative error (there is no response) The response the host will receive during a complete pass through a Search ROM function using the Search Accelerator consists of 16 bytes as follows: ...
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... DS2480B to the host. The remaining three parameters are used to modify the 1-Wire communication waveforms if one selects “ ...
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... POL pin (asymmetry bit, see Figure 1). This may reduce the component count in some applications of the device. Note that when changing the baud rate, the DS2480B will send the command response byte at the new data rate. A short explanation on the use of parameters 100 (Write-1 Low Time) and 101 (Data Sample Offset/Write-0 Recovery Time) is given in the Timing Diagrams section later in this document ...
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Table 4. CONFIGURATION PARAMETER VALUE CODES Parameter Code 000 001 (PDSRC) 15 010 (PPD) 32 011 (SPUD) 16.4 100 (W1LT) 8 101 (DSO/W0RT) 3 110 (LOAD) 1.8 111 (RBR) 9.6 The syntax of configuration commands is very simple. Each 8-bit ...
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... Figure 4. ACTIVE PULLUP The circuit operates as follows From this point on the 1-Wire bus is pulled high by the weak pullup current I DS2480B. The slope is determined by the load on the bus and the value of the pullup current voltage crosses the threshold voltage V current I to the higher current I ...
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... Falling Edges (DS2480B-initiated) Whenever the DS2480B begins pulling the 1-Wire bus low to initiate a time slot, for example, it first turns off the weak pullup current I edge at a slew rate of typically 15V/ms. This value is acceptable for short 1-Wire busses and adequate for communication at Overdrive speed. For MicroLAN networks of more than roughly 30m length one should always use flexible speed ...
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... DS2480B will then wait for t response byte to the host. If the test for interrupt or short reveals a logic 0, the DS2480B will wait for 4096ms and then test the 1-Wire bus again logic 0 is detected, the 1-Wire bus is shorted and a command response byte with the code for SHORT will be sent immediately ...
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... Therefore, the timing generated by the DS2480B is in compliance with the requirements of all MicroLAN- compatible 1-Wire devices. ...
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... Figure 7b. 12V PROGRAMMING PULSE, PREDEFINED DURATION A correct programming pulse can only be generated if the 12V programming voltage is available at the V pin of the DS2480B. The rising and falling edges of the programming pulse are actively controlled by PP DS2480B. The slew rate is approximately 14V/µs and meets the requirements of 1-Wire EPROM devices ...
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... Selecting infinite duration allows the host to generate pulses of any length consequence, however, the host becomes responsible to actively control the duration of the pulse. Failing may require a power-on reset or master reset cycle of the DS2480B. For this reason, infinite duration should only be used if absolutely necessary. ...
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... Figure 8. STRONG PULLUP TO 5V, ARMED, PREDEFINED DURATION Figures 8 shows the timing of the strong pullup in Data Mode 1-Wire bus is completed. Without any delay the DS2480B now activates the strong pullup and simultaneously starts sending the data response byte to the host DS2480B sends a pulse response byte to the host. The idle time between t to transmit the pulse response byte, plus the response time of the host plus the time to transmit the command and/or data to generate the next time slot ...
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... The strong pullup of the Single Bit command, however, is controlled directly by bit 1 of the command code and therefore needs not be armed. Since the DS2480B remains in Command Mode when using the Single Bit command, any duration of the strong pullup including dynamic as well as infinite may be selected ...
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... The response byte on the reset command assumes a normal presence pulse, no alarm or short. The DS2480B includes a 1-byte buffer that stores a byte received from the host while the previous byte is being translated into activity on the 1-Wire bus. For this reason the host may send another byte even without having received the response byte ...
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READ MEMORY SEQUENCE Action Sequence Generate Reset Pulse Set Data Mode Skip ROM Command Read Memory Command Starting Address TA1 Starting Address TA2 Read 8 Bytes of Data Set Command Mode Generate Reset Pulse WRITE EPROM SEQUENCE (DS2505) Write memory ...
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... Figure 10. R-C FILTERING protect the 1-Wire port of the DS2480B from electrostatic discharge it is recommended to use a low- capacitance ESD protection diode, such as the DS950x devices. For 5V operation a single device is sufficient. For EPROM programming two DS950x devices must be connected in series to achieve a high enough breakdown voltage ...
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... Start 0 The signals DTR and RTS provide the power to operate the DS2480B. The resistor in the TXD line and the Schottky diode limit the negative voltage at the TXD pin of the DS2480B to 0.3V maximum. The resistor is typically 4.7kW. If the inverting driver is current-limited to 1mA the resistor is not required. ...
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... Start 0 In the interface to a true RS232C system (±12V, Figure 11c) the power for the DS2480B is stolen from DTR and RTS. The software must make sure that at least one of these signals constantly provides the 12V operating voltage. The 6.8kW resistor and the 4.7V Zener diode in the TXD line limit the positive voltage at the TXD pin of the DS2480B ...
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... The +5V are sufficient for most RS232C systems. Switching in 12V requires an opto-isolator with different voltage characteristics. In the schematic the HCPL-2202 opto-isolator is sourced by the RXD pin of the DS2480B. It can as well be connected the traditional way where the DS2480B sinks the current through the LED. This, however, causes a signal inversion that has to be compensated through the DS2480B by using a value code of 100, 101, 110, or 111 for the RS232 baud rate setting ...
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Figure 12. RS232 DATA TIMING RXD LINE Figure 13. RECEIVE DELAY TIMING Figure 14. RS232 DATA TIMING TXD LINE Figure 15. TXD LINE ASYMMETRY ...
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Table 7. FUNCTION AND SPEED MATRIX Baud Rate 9600bps 19200bps 57600bps 115200bps √ guaranteed by the UART; no precautions necessary. IDLET X Not recommended unless t 1-Wire Speed Regular Flexible √ √ √ √ √ X ...
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ABSOLUTE MAXIMUM RATINGS* Voltage on 1-W to Ground Voltage on RXD, TXD, POL to Ground Operating Temperature Range Storage Temperature Range Soldering Temperature * This is a stress rating only and functional operation of the device at these or any ...
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... Overdrive speed the capacitive load on the 1-Wire bus must not exceed 1nF. 16. Baud rate calibration is valid at a static V than 5% may cause calibration error to exceed 5%. The DS2480B requires a 1-Wire reset command sent by the host at a data rate of 9600bps for calibration. Data rates of 115200bps or higher during calibration may put the DS2480 in an undefined state, requiring a power-down reset to restore normal operation ...