feature

10-bit ADC with 15µs and 30µs conversion times; single-ended and 4 single-ended analog input channels; on-chip temperature sensor: –40°C to + 125 °C; on-chip track and hold; power supply; wide operating supply range: 2.7 V to 5.5 V; I2C compatible serial interface; selectable serial bus address allows connection of up to 8; AD7416 /AD7417 devices to a single bus; AD7416 is the best replacement for the LM75 .

application

Ambient temperature monitoring data acquisition; industrial process control; automotive; battery charging applications; personal computers.

General Instructions

The AD7417 and AD7418 are 10-bit, 4-channel and single-channel ADCs with an on-chip temperature sensor that can operate from a single 2.7 V to 5.5 V supply. The device contains a 15µs successive approximation converter, a 5-channel multiplexer, a temperature sensor, clock oscillator, track and hold, and reference voltage (2.5 volts). The AD7416 is only used for temperature monitoring devices in an 8-wire package.

The temperature sensor on the part is accessible through multiplexer channel 0. When channel 0 is selected and a conversion is started, the resulting ADC code at the end of the conversion measures the ambient temperature (±1°C@25°C). On-chip registers can program high and low temperature limits and an open circuit over temperature indicator (OTI) provides an output when the programmed limits are exceeded.

The configuration registers allow programming of the meaning of the OTI output (active high or active low) and its mode of operation (comparator or interrupt). A programmable fault queue counter allows the number of out-of-limit measurements that must occur before triggering the OTI output to be set to prevent false triggering of the OTI output in noisy environments.

The IC®-compatible serial interface allows the AD7416/AD7417/AD7418 registers to be written to and read from. The three LSBs of the AD7416/AD7417 serial bus address can be selected, which allows up to eight AD7416/AD7417 devices to be connected to one bus.

The AD7417 is available in a narrow-body, 0.15-inch, 16-lead, small outline package (SOIC) and a 16-lead, thin shrink, small outline package (TSSOP). The AD7416 and AD7418 are available in 8-lead SOIC and MSOP packages.

Product Highlights

1. The AD7416/AD7417/AD7418 have an on-chip temperature sensor that can accurately measure the ambient temperature (±1°C@25°C, ±2°C overheating). The measurable temperature range is -40°C to +125°C. An overtemperature indicator is implemented by digitally comparing the ADC code of channel 0 (temperature sensor) with the contents of the on-chip T setpoint register.

2. The AD7417 provides a space-saving 10-bit analog-to-digital solution with four external voltage input channels, an onboard temperature sensor, an on-chip reference, and a clock oscillator.

3. The automatic power-off function enables AD7416/AD7417/AD7418 to obtain excellent power performance. At lower production rates, the part can be programmed to operate in a low-power shutdown mode for further power savings.

the term

Relative accuracy

Relative accuracy or endpoint nonlinearity is the maximum deviation from a straight line through the endpoints of the ADC transfer function.

Differential nonlinearity

This is the difference between the measured value and the ideal 1 LSB change between any two adjacent codes in the ADC.

offset error

This is the deviation of the first code transition (0000…000) to (0000…001) from the ideal (ie GND + 1 LSB).

offset error matching

This is the offset error difference between any two channels.

gain error

This is the deviation of the last code transition (1111…110) to (1111…111) from the ideal (ie VREF 8722 ; 1 LSB) after the offset error has been adjusted.

Gain Error Matching

This is the difference in gain error between any two channels.

Track and hold acquisition time

Track and hold acquisition time is the time it takes for the output of the track and hold amplifier to reach its final value, within ±1/2 LSB, after the transition ends (the point at which track and hold returns to track mode). It also applies when there is a change in the selected input channel, or when there is a step input change in the input voltage applied to the a input of the selected AD7417 or AD7418. This means that the user must wait for the duration of the track and hold acquisition time after the conversion ends, or after a channel change or step input change to a, before starting another conversion to ensure the part is working to specification.

theory of operation

circuit information

The AD7417 and AD7418 are single- and quad-channel, 15µs conversion time, 10-bit ADCs with on-chip temperature sensor, reference, and serial interface logic. The AD7416 has no analog input channels and is only used for temperature measurements. The ADC section consists of a conventional successive approximation converter around a capacitor DAC. The AD7416, AD7417, and AD7418 are capable of operating from a 2.7 V to 5.5 V supply, and the AD7417 and AD7418 accept an analog input range of 0 V to +VREF. On-chip temperature sensors allow accurate measurement of ambient device temperature. The operating measurement range of the temperature sensor is -40°C to +125°C. The part requires a reference voltage of 2.5 V, which can be supplied from the part's own internal voltage reference or from an external reference voltage source.

Converter Details

The input is converted by pulse on the AD7417/AD7418. The conversion clock for the part is internally generated, so no external clock is required, except when reading from and writing to the serial port. The on-chip track and hold transition sequence from track mode to hold mode begins on the falling edge of the CONVST signal. A conversion is also initiated in auto-conversion mode each time a read or write operation is performed on the AD7416/AD7417/AD7418. In this case, the internal clock oscillator (running an automatic conversion sequence) restarts at the end of a read or write operation. After a read or write operation is complete, the track and hold enters hold mode for approximately 3 μs, and then begins the conversion. The conversion result is available after 15µs or 30µs, depending on whether an analog input channel or a temperature sensor is selected. The track-and-hold acquisition time of the AD7417/AD7418 is 400ns.

Temperature measurements are made by selecting channel 0 of the on-chip mux and converting on this channel. The conversion on channel 0 takes 30µs to complete. Temperature measurements are described in the "Temperature Measurements" section.

The on-chip reference is not available to the user, but an external reference source (2.5 V only) can overdraw the reference. All unused analog inputs should be connected to a voltage within the nominal analog input range to avoid noise pickup. To reduce power consumption, unused analog inputs should be connected to GND.

Typical Wiring Diagram

Figure 9 shows a typical connection diagram for the AD7417. If desired, the user can select up to eight AD7417 devices on the same serial bus using the A0, A1, and A2 pins. An external 2.5 V reference can be connected at the reference pin. If using an external reference, a 10µF capacitor should be connected between REF and GND. SDA and SCL form a 2-wire IC compatible interface. For applications involving power consumption, automatic power-down at the end of conversion should be used to improve power performance (see the Operating Modes section).

analog input

Figure 10 shows the structure of the AD7417 and AD7418 equivalent circuits for analog inputs. Two diodes D1 and D2 provide ESD protection for the analog inputs. Care must be taken to ensure that the analog input signal does not exceed the supply rails by more than 200 mV to prevent these diodes from being forward biased and starting to conduct current to the substrate. These diodes can draw up to 20mA without irreversible damage. Capacitor C2 in Figure 10 is typically around 4pF, mainly due to pin capacitance. Resistor R1 is a lumped element consisting of the on-resistance of the multiplexer and switch. This resistance is typically around 1kΩ. Capacitor C1 is the ADC sampling capacitor, and its capacitance is 3pf.

on-chip reference

The AD7417/AD7418 have an on-chip bandgap reference of 1.2V that is amplified by a switched capacitor amplifier to provide a 2.5V output. The amplifier is powered up only at the beginning of the conversion phase and de-energized at the end of the conversion. The on-chip reference is selected by connecting the REF pin to analog ground, which will cause SW1 (see Figure 11) to open during conversions and power up the reference amplifier. Therefore, the on-chip reference cannot be obtained externally. An external 2.5 V reference can be connected to the reference pin. This causes the on-chip reference circuit to shut down.

temperature measurement

A common method of measuring temperature is to use the negative temperature coefficient of a diode or the base-emitter voltage of a transistor, operating at a constant current. Unfortunately, this technique requires calibration to remove the effect of the absolute value of V, which varies from device to device. The technique used in the AD7416/AD7417/AD7418 is to measure the current change in V when the device is operated at two different currents.

This is done by:

where: K is the Boltzmann constant. q is the charge on the electron (1.6 x 10-19 coulombs). T is the absolute temperature in Kelvins. N is the ratio of the two currents.

Figure 12 shows the method used by the AD7416/AD7417/AD7418 to measure device temperature. To measure ΔV, the sensor (substrate transistor) switches between I and N×I operating currents. The resulting waveform is passed through a chopper-stabilized amplifier, which performs the functions of amplifying and rectifying the waveform to produce a DC voltage proportional to ΔV. This voltage is measured by a dc to give the temperature output in 10-bit 2's complement form.

The temperature resolution of the ADC is 0.25°C, which corresponds to 1 LSB of the ADC. The ADC can theoretically measure a temperature range of 255°C; the guaranteed temperature range is -40°C to +125°C. The conversion result is stored in the temperature value register (0x00) as a 16-bit word. The 10 MSBs of this word store temperature measurements (see Tables 9 and 10).

The temperature conversion formula using the 10 MSBs of the temperature value register is as follows:

Remove the MSB from the ADC code in Equation 2.

Internal register structure

The AD7417/AD7418 have seven internal registers, as shown in Figure 13. Six of them are data registers and one is an address pointer register. The AD7416 has five internal registers (the ADC and Config2 registers do not apply to the AD7416).

address pointer register

The address pointer register is an 8-bit register that stores an address pointing to one of the six data registers. The first data byte of each serial write operation to the AD7416/AD7417/AD7418 is the address of one of the data registers stored in the address pointer register and selects the data register to which subsequent data bytes are written. Only the three LSBs of the address pointer register are used to select the data register.

Temperature Value Register (Address 0x00)

The temperature value register is a 16-bit read-only register whose 10 MSBs store the temperature data read from the ADC in 10-bit two's complement format. Bits D5 to D0 are unused.

The temperature data format is shown in Table 10. This shows the full theoretical range of the ADC from -128°C to +127°C, but in practice the temperature measurement range is limited to the operating temperature range of the device.

Configuration Register (Address 0x01)

The configuration register is an 8-bit read/write register that sets the operating mode of the AD7416/AD7417/AD7418. Bits D7 to D5 control the channel selection, as shown in Table 12. Bits[D7:D5] of the AD7416 should always be set to 000. Bit D4 and Bit D3 are used to set the length of the fault queue. D2 sets the meaning of the OTI output. D1 selects the comparator or interrupt operation mode, and D0=1 selects the shutdown mode (default: D0=0).

The AD7416 contains one temperature-only channel; the AD7417 has four analog input channels and one temperature channel; the AD7418 has two channels, one temperature channel and one analog input channel. All components have the same temperature channel address, channel 0. The address of the analog input channel on the AD7418 is channel 4. Table 12 summarizes the channel selection on the part, and Table 13 shows the fault queue settings. D1 and D2 are explained in the OTI output section.

THYST Setpoint Register (Address 0x02)

The THYST setpoint register is a 16-bit read/write register whose nine MSBs store the THYST setpoint in two's complement format equivalent to the nine MSBs of the temperature value register. Bits D6 to D0 are unused.

TOTI Set Value Register (Address 0x03)

The TOTI setpoint register is a 16-bit read/write register whose nine MSBs store the TOTI setpoint in two's complement format equivalent to the nine MSBs of the temperature value register. Bits 6 to 0 are unused.

ADC Value Register (Address 0x04)

The ADC value register is a 16-bit read-only register whose 10 MSBs store the value produced by the ADC in binary format. Bits D5 to D0 are unused. Table 15 shows the ADC value register containing the 10 MSBs of the ADC conversion request.

ADC transfer function

The designed transcoding occurs at consecutive integer LSB values (ie 1 LSB, 2 LSB, etc.). LSB size = VREF/1024. The ideal transfer function characteristics of the AD7417 and AD7418 ADCs are shown in Figure 14.

Configuration 2 Register (Address 0x05)

A second configuration register/AD7418 is included in the AD7417 for the functionality of the CONVST pin. It is an 8-bit register with bits D5 to D0 held at 0. Bit D7 determines whether the AD7417/AD7418 should operate in its default mode (D7=0), performing a conversion every 355 μs, or in its CONVST pin mode (D7=1), where conversions only begin when the CONVST pin is used. Bit 6 contains the test 1 bit. When this bit is 0, the IC filter is enabled (default). Setting this bit to 1 will disable the filter.

serial bus interface

Control of the AD7416/AD7417/AD7418 is performed through an IC-compatible serial bus. The AD7416/AD7417/AD7418 are connected to this bus as slave devices under the control of a master device such as a processor.

serial bus address

Like all IC-compatible devices, the AD7416/AD7417/AD7418 have a 7-bit serial address. The four most significant bits of this address for the AD7416 are set to 1001; the AD7417 is set to 0101, and the user can set the three least significant bits by connecting the A2 to A0 pins to V or GND. Up to eight AD7416/AD7417 devices can be connected to a single serial bus by giving them different addresses, or these addresses can be set to avoid conflicts with other devices on the bus. AD7418 The four msbs of this address are set to 0101 and the three lsbs are all set to 0.

If serial communication occurs during a conversion operation, the conversion will stop and restart after the communication.

The serial bus protocol operates as follows:

1. The host initiates a data transfer by establishing a start condition, defined as a high-to-low transition on the serial data line SDA, while the serial clock line SCL remains high. This means that an address/data stream follows. All slave peripherals connected to the serial bus respond to a 7-bit address (MSB first) plus an R/W bit that determines the direction of data transfer, i.e. whether data is written to or read from the slave.

The peripheral whose address corresponds to the address sent responds by pulling the data line low during the low cycle before the ninth clock pulse (called the acknowledge bit). All other devices on the bus are now idle while the selected device is waiting to read or write data from it. If the R/W bit is 0, the master device writes to the slave device. If the R/W bit is 1, the master device reads from the slave device.

2. Data is sent over the serial bus in a sequence of 9 clock pulses, 8 bits of data followed by an acknowledgment bit from the data receiver. Transitions on the data line must occur during the low period of the clock signal and remain stable during the high period because a low-to-high transition while the clock is high can be interpreted as a stop signal.

3. A stop condition is established when all data bytes are read or written. In write mode, the master asserts a stop condition by pulling the data line high during the 10th clock pulse. In read mode, the master device pulls the data line high for a low period before the ninth clock pulse. This is called non-recognition. The master then asserts the stop condition by taking the data line low during the low period before the 10th clock pulse and then high during the 10th clock pulse.

In one operation, any amount of data can be transferred over the serial bus, but it is not possible to mix reads and writes in one operation because the operation type is determined at the beginning and cannot be done without starting a new operation Subsequent changes.

Write to AD7416/AD7417/AD7418

The AD7416/AD7417/AD7418 can be written in three different ways, depending on the register being written to.

(1) Write the address pointer register for subsequent reading. To read data from a specific register, the address pointer register must contain the address of that register. If not, the correct address must be written to the address pointer register by performing a single-byte write operation, as shown in Figure 15. A write operation consists of the serial bus address and address pointer bytes. No data is written to any data registers.

(2), write single-byte data into the configuration register, configuration 2 register or T set point or T set point register.

The configuration register is an 8-bit register, so only one byte of data can be written to it. If only 8-bit temperature comparisons are required, the temperature LSB can be ignored in T and T, and only 8 bits need to be written to the T-setpoint and T-setpoint registers. Writing a single byte of data to one of these registers consists of the serial bus address, the data register address written to the address pointer register, and the data byte written to the selected data register. As shown in Figure 16.

(3) Write a two-byte data set value register to the TOTI set point or THYST. If the temperature setpoint requires 9-bit resolution, two bytes of data must be written to the TOTI setpoint and THYST setpoint registers. This includes the serial bus address, the register address register where the address pointer is written, followed by the data register where the two data bytes are written to the selected object. As shown in Figure 17.

Read data from AD7416/AD7417/AD7418

Reading data from the AD7416/AD7417/AD7418 is a single-byte or double-byte operation. Reading the contents of the configuration register is a single-byte read operation, as shown in Figure 18, the register address was previously set by a single-byte write operation to the address pointer register.

When reading data from the temperature value register, the Tsetpoint or Tsetpoint register is a 2-byte operation, as shown in Figure 19. The most significant bits of a 9-bit or 10-bit register can also be read this way.

Note that when reading data from the AD7416/AD7417/AD7418, no more than three bytes of data must be read. A stop command must be inserted at the end of the read communication. If a stop command is not inserted by the host and the AD716/AD717/AD718 receives more SCL cycles than the maximum required for three bytes of data, the IC interface on the AD716/AD717/AD718 pulls the SDA line low and prevents it from again high level. To restore the AD7416/AD7417/AD7418 interface, the part must be turned off and on again. For more information on IC interfaces, see the AN-686 application note, Implementing I on .

OTI output

The OTI output has two modes of operation, determined by bit D1 of the configuration register. In comparator mode, (D1=0), when the temperature exceeds T, the OTI output becomes active and remains active until the temperature falls below T. This mode allows the AD7416/AD7417/AD7418 to be used as a thermostat, for example, to control the operation of a cooling fan.

The open-drain configuration of OTI allows the OTI outputs of several AD7416/AD7417/AD7418 devices to be tied together when low mode is active.

The OTI output is used to indicate that an out-of-limit temperature excursion has occurred. OTI is an open-drain output that can be programmed to be active low by setting Bit D2 of the Configuration Register to 0 or by setting Bit D2 of the Configuration Register to 1.

In interrupt mode (D1=1), the OTI output activates when the temperature exceeds T, even if the temperature falls below T, until reset by a read operation. Once the OTI is activated and reset due to a temperature exceeding T, it will remain inactive even if the temperature remains above T or subsequently rises again. It does not activate again until the temperature drops below T. It will then remain active until reset by a read operation. Once the OTI is activated by the temperature falling below T and then reset, it remains inactive even if the temperature remains or subsequently falls below T again.

The OTI is also reset by setting Bit D0 of the configuration register to 1 when the AD7416/AD7417/AD7418 are in shutdown mode.

The OTI output requires an external pull-up resistor. This can be connected to a different voltage than V (for example, to allow interfacing between 5 V and 3.3 V systems), as long as the maximum voltage rating of the OTI output is not exceeded.

The value of the pull-up resistor is application dependent, but should be as large as possible to avoid excessive sink current at the OTI output, which would heat the chip and affect temperature readings. The maximum value for a pull-up resistor that meets the output high current specification for the OTI output is 30 KΩ, but higher values can be used if lower output current is required. A value of 10 kΩ is suitable for most applications.

failure queue

To avoid false triggering of the AD7416/AD7417/AD7418 in noisy environments, a fault queue counter is provided that can be programmed by Bit D3 and Bit D4 of the configuration register (see Table 11) to count 1, 2, 4 before OTI activation or 6 failure events. To trigger OTI, faults must occur continuously. For example, if the fault queue is set to 4, then four consecutive temperature measurements greater than T (or less than T) must be made. Any interrupted sequence of reads resets the fault queue counter, so if there are three reads greater than T followed by a read less than T, the fault queue counter will reset without triggering an OTI.

boot default

The AD7416/AD7417/AD7418 always power up with the following default values:

(1), the address pointer comparator mode pointing to the temperature value register;

(2), the total temperature = 80 ° C;

(3), THYST=75 degrees Celsius;

(4), OTI activity is low;

(5), fault queue = 1;

These default settings allow the AD7416/AD7417/AD7418 to be used as a stand-alone thermostat without connecting to a serial bus.

Operating mode

Depending on the value of D0 in the configuration register, the AD7416/AD7417/AD7418 have two possible modes of operation.

Mode 1

When D0=0, the AD7416/AD7417/AD7418 work normally. In this active mode, a conversion occurs every 400µs. After the conversion is complete, the part is partially powered down, typically consuming 350µA, until the next conversion occurs.

There are two possible scenarios for this mode depending on the requirements of the temperature reading. If a read occurs during a conversion, the conversion is aborted and a new read is initiated under a stop/restart condition. The temperature value read is the temperature value of the previously completed conversion. The next conversion usually occurs 400µs after the start of a new conversion.

If read is called between conversions, the conversion is started on a stop/repeated start condition. After this conversion, the part returns to performing conversions every 400 μs.

The AD7416/AD7417/AD7418 spend 40µs (or 10% of the time) in conversion mode when V=3v per 400µs cycle. The part spends 360µs (or 90% of the time) in partial power down mode. Therefore, the average power dissipation of the AD7416/AD7417/AD7418 is:

Mode 2

For applications that require temperature measurement at a slower rate, eg, per second, power consumption can be reduced by powering down between partial reads by writing to parts. The current consumption of full power down is usually 0.2μA, and start full power down when D0=1 in the configuration register. When the measurement value is required, a write operation can be performed to make a section. The component then performs a transition and returns to power down. The temperature value can be read with complete power down because the I2C bus is continuously active.

Power consumption in this mode depends on the read taking place. Measured every 100ms based on temperature requirements, taking the best power loss as an example is achieved by powering down the part completely, waking it up every 100ms, letting it work for 400µs and shutting it down completely again. In this case, the average power consumption is calculated as follows. Parts take 40µs (or 0.04% of the time) to convert, 3mW dissipated in 99.96 ms (99.96% of the time) dissipated completely off at 60 nW.

Therefore, the average power consumption is:

The fastest throughput of the AD7416/AD7417/AD7418 operates at 2.5 kHz (i.e. a conversion period is read every 400µs). Because TOTI and THYST are 2-byte reads, using I2 read time C running at 100 kbps would be 270µs. If the temperature readings are too frequent, the readings will switch with each other, constantly aborting them, resulting in invalid readings.

switch boot mode

The AD7417/AD7418 have an additional mode that is set by writing to the MSB of the Config2 register.

switch pin mode

Conversion is only initiated by using the CONVST pin. In this method of operation, CONVST is usually low. The rising edge of CONVST begins the power-up time. This power-on time is 4 μs. If the CONVST high time is greater than 4μs, the falling edge of convs starts to convert the trace and hold also enters its hold mode. If the CONVST high time is less than 4μs, the internal timer, started by the rising edge of CONVST, keeps track and hold, and starts the conversion until the timer counts the output (4μs after the rising edge of convs, corresponding to the power-up time). The CONVST input is held low at the end of a conversion, causing the part to enter shutdown mode. In this method of operation, CONVST is normally low and high pulses control the power supply, and the conversion begins.

When reading from or reading, the CONVST pin should not pulse the port being written to. Figure 21 shows the conversion pulse when the temperature channel is selected. Figure 22 shows the minimum number of analog input channels picked out.

application information

Power decoupling

The AD7416/AD7417/AD7418 should be separated with a 0.1µF ceramic capacitor between V and GND. This is especially important if the components are installed away from the power source.

power-on reset

To ensure proper power-on reset, make sure that the voltage on the power supply V pin is 0 V. For more information, see the AN-588 Application Note, AD7416/AD7417/AD7418 Power-On Reset Circuits. A power-on reset failure prevents default values from being loaded into the AD7416/AD7417/AD7418 registers. If the correct value is not loaded into the register, the device cannot start functioning. The output of the temperature value and ADC value registers will be a constant value.

To restart device operation, the registers must be loaded with their default values via the IC bus. Therefore, in the event of insufficient power-on-reset, the following registers should be loaded with their default values for all three devices:

(1), the default value of the configuration register = 0x00;

(2), Config2 register default value = 0x00;

(3), T set point register default value = 0x4B00;

(4) The default value of T set point register = 0x5500.

Install the AD7416/AD7417/AD7418

The AD7416/AD7417/AD7418 can be used in surface or air temperature sensing applications. If a thermally conductive adhesive is used to bond the device to the surface, the mold temperature is around 0.2°C of the surface temperature due to the low power consumption of the device. If the ambient air temperature is different from the surface temperature being measured, take care to insulate the back of the device and the leads from the air.

The ground pins provide the best thermal path to the die, so the temperature of the die is close to the temperature of the printed circuit ground track. Take care to ensure that it is in close contact with the surface being measured.

As with any integrated circuit, the AD7416/AD7417/AD7418 and its associated wiring and circuitry must be kept protected from moisture to prevent leakage and corrosion, especially in cold conditions where condensation is more likely to occur. Water-resistant varnishes and conformal coatings can be used for protection. The small size of the AD7416 package allows it to be mounted within a hermetically sealed metal probe, providing a safe environment for the device.

fan controller

Figure 23 shows a simple fan controller that turns on a cooling fan when the temperature exceeds 80°C and turns off again when the temperature falls below 75°C. If a different trip temperature is required, the AD7416 can be used as a stand-alone device in this application, or used with a serial bus interface. If the AD7416 is used with a bus interface, the OTI's sense can be set active high, Q1 and R1 can be omitted, and the OTI can be connected directly to the gate of Q2 with R2 as a pull-up resistor.

Thermostat

Figure 24 shows the AD7416 used as a thermostat. When the temperature is lower than T, the heater is turned on, and when the temperature is higher than T, the heater is turned off again. For this application and comparator mode, set the OTI output to active low.

Systems with Multiple AD7416 Devices

The three LSBs of the AD7416 serial address can be set by the user, allowing eight different addresses from 1001000 to 1001111. Figure 25 shows a system in which eight AD7416 devices are connected together to form a common interrupt line through their OTI connections to a single serial bus output line. This arrangement means that each device must be read to determine which device generated the interrupt, and if each device needs a unique interrupt, the OTI outputs can be individually connected to the I/O chips.

Dimensions