| Smartcat (BL2100) User's Manual |
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3. Subsystems
Chapter 3 describes the principal subsystems for the BL2100.
- · Digital I/O
- · Serial Communication
- · A/D Converter Inputs
- · D/A Converter Outputs
- · Analog Reference Voltage Circuit
- · Memory
- · External Interrupts
Figure 7 shows these Rabbit-based subsystems designed into the BL2100.
3.1 BL2100 Pinouts
The BL2100 pinouts are shown in Figure 8.
NOTE Screw-terminal header J1 and the associated analog I/O are not available on the BL2110 and the BL2130. 3.1.1 Headers and Screw Terminals
Standard BL2100 models are equipped with two 1 × 12 screw terminal strips (J7 and J13), and two 1 × 14 screw terminal strips (J4 and J11). The BL2100 and BL2110 also have the RJ-45 Ethernet jack and one 1 × 16 screw terminal strip (J1).
There is provision on the circuit board to accommodate 2 × 17, 2 × 20, and 2 × 25 male headers instead of the screw terminal strips supplied, and the male headers can be factory-installed by special request for volume orders. Contact your Z-World Sales Representative at +1(530)757-3737 for more information.
3.2 Digital I/O
3.2.1 Digital Inputs
The BL2100 has 24 digital inputs, IN00-IN23, each of which is protected over a range of -36 V to +36 V. The inputs are factory-configured to be pulled up to +5 V, but they can also be pulled up to +K2 or down to 0 V in banks of eight by changing a surface-mounted 0 W resistor as shown in Figure 9.
NOTE If the inputs are pulled up to +K2, the voltage range over which the digital inputs are protected changes to K2 - 36 V to +36 V. The actual switching threshold is approximately 2.40 V. Anything below this value is a logic 0, and anything above is a logic 1.
IN16-IN23 can be factory-configured as outputs for users who prefer to have 16 inputs and 24 outputs.
3.2.2 Digital Outputs
The BL2100 has 16 digital outputs, OUT00-OUT15, which can each sink or source up to 200 mA. Figure 10 shows a wiring diagram for using the digital outputs in a sinking or a souring configuration.
All the digital outputs sink and source actively. They can be used as high-side drivers, low-side drivers, or as an H-bridge driver. When the BL2100 is first powered up or reset, all the outputs are disabled, that is, at a high-impedance status, until the digoutConfig software function call is made. The digoutConfig call sets the initial state of each digital output according to the configuration specified by the user, and enables the digital outputs to their initial status.
OUT00-OUT07 are powered by to +K1, and OUT08-OUT15 are powered by +K2. K1 and K2 can each be up to 36 V. They don't have to be same.
All the sinking current, which could be up to 3.2 A, is returned through the GND pins. Be sure to use a suitably sized GND and keep the distance to the power supply as short as possible. Since there are two GND terminals (pin 1, screw-terminal header J4, and pin 12, screw-terminal header J11), it is highly recommend that you split the GND returns according to the two banks of digital outputs.
For the H bridge, which is shown in Figure 11, K1 and K2 should be the same if two digital outputs used for the H bridge are on different banks.
3.3 Serial Communication
The BL2100 has two RS-232 serial ports, which can be configured as one RS-232 serial channel (with RTS/CTS) or as two RS-232 (3-wire) channels using the serMode software function call. Table 2 summarizes the options.
Table 2. Serial Communication Configurations 0 RS-232, 3-wire RS-232, 3-wire RS-485 1 RS-232, 5-wire CTS/RTS RS-485 The BL2100 also has one RS-485 serial channel and one CMOS serial channel that serves as the programming port.
All four serial ports operate in an asynchronous mode. An asynchronous port can handle 7 or 8 data bits. A 9th bit address scheme, where an additional bit is sent to mark the first byte of a message, is also supported. Serial Port A, the programming port, can be operated alternately in the clocked serial mode. In this mode, a clock line synchronously clocks the data in or out. Either of the two communicating devices can supply the clock. The BL2100 boards typically use all four ports in the asynchronous serial mode. Serial Ports B and C are used for RS-232 communication, and Serial Port D is used for RS-485 communication. The BL2100 uses an 11.0592 MHz crystal, which is doubled to 22.1184 MHz. At this frequency, the BL2100 supports standard asynchronous baud rates up to a maximum of 230,400 bps.
3.3.1 RS-232
The BL2100 RS-232 serial communication is supported by an RS-232 transceiver. This transceiver provides the voltage output, slew rate, and input voltage immunity required to meet the RS-232 serial communication protocol. Basically, the chip translates the Rabbit 2000's CMOS/TTL signals to RS-232 signal levels. Note that the polarity is reversed in an RS-232 circuit so that a +5 V output becomes approximately -10 V and 0 V is output as +10 V. The RS-232 transceiver also provides the proper line loading for reliable communication.
RS-232 can be used effectively at the BL2100's maximum baud rate for distances of up to 15 m.
3.3.2 RS-485
The BL2100 has one RS-485 serial channel, which is connected to the Rabbit 2000 Serial Port D through an RS-485 transceiver. The half-duplex communication uses the Rabbit 2000's PB6 pin to control the transmit enable on the communication line.
The BL2100 can be used in an RS-485 multidrop network. Connect the 485+ to 485+ and 485- to 485- using single twisted-pair wires (nonstranded, tinned) as shown in Figure 12. Note that a common ground is recommended.
The BL2100 comes with a 220 W termination resistor and two 681 W bias resistors installed and enabled with jumpers across pins 1-2 and 5-6 on header JP1, as shown in Figure 13.
For best performance, the bias and termination resistors in a multidrop network should only be enabled on both end nodes of the network. Disable the termination and bias resistors on any intervening BL2100 units in the network by removing both jumpers from header JP1.
NOTE Save the jumpers for possible future use by "parking" them across pins 1-3 and 4-6 of header JP1. Pins 3 and 4 are not otherwise connected to the BL2100. 3.3.3 Programming Port
The RabbitCore module on the BL2100 has a 10-pin programming header. The programming port uses the Rabbit 2000's Serial Port A for communication, and is used for the following operations.
- Programming/debugging
- Cloning
- Remote program download/debug over an Ethernet connection via the RabbitLink EG2100
The programming port is used to start the BL2100 in a mode where the BL2100 will download a program from the port and then execute the program. The programming port transmits information to and from a PC while a program is being debugged.
The Rabbit 2000 startup-mode pins (SMODE0, SMODE1) are presented to the programming port so that an externally connected device can force the BL2100 to start up in an external bootstrap mode. The BL2100 can be reset from the programming port via the /EXT_RSTIN line.
The Rabbit 2000 status pin is also presented to the programming port. The status pin is an output that can be used to send a general digital signal.
NOTE Refer to the Rabbit 2000 Microprocessor User's Manual for more information related to the bootstrap mode. 3.3.4 Ethernet Port
Figure 14 shows the pinout for the Ethernet port (J2 on the BL2100 module). Note that there are two standards for numbering the pins on this connector--the convention used here, and numbering in reverse to that shown. Regardless of the numbering convention followed, the pin positions relative to the spring tab position (located at the bottom of the RJ-45 jack in Figure 14) are always absolute, and the RJ-45 connector will work properly with off-the-shelf Ethernet cables.
RJ-45 pinouts are sometimes numbered opposite to the way shown in Figure 14.
Two LEDs are placed next to the RJ-45 Ethernet jack, one to indicate an Ethernet link (LNK) and one to indicate Ethernet activity (ACT).
The transformer/connector assembly ground is connected to the BL2100 module printed circuit board digital ground via a 0 W resistor "jumper," R29, as shown in Figure 15.
The factory default is for the 0 W resistor "jumper" at R29 to be installed. In high-noise environments, remove R29 and ground the transformer/connector assembly directly through the chassis ground. This will be especially helpful to minimize ESD and/or EMI problems.
3.4 A/D Converter Inputs
The single 14-channel A/D converter used in the BL2100 has a resolution of 12 bits (models BL2100 and BL2120 only). Eleven of the 14 channels are available externally, and three are used internally for the reference voltages: 4.096 V (Vref), 2.048 V (Vref/2), and Analog Ground. These internal voltages can be used to check the functioning of the A/D converter.
The A/D converter only measures voltages between 0 V and the applied reference voltage. Therefore, each external input has circuitry that provides scaling and buffering. All 11 external inputs are scaled and buffered to provide the user with an input impedance of 1 MW and a range of -10.24 V to +10.24 V.
Figure 16 shows the buffered A/D converter inputs.
The op-amp is powered from the +V supply. The 1 MW and 200 kW resistors set the gain (scale factor), which is 0.2 in this case. This results in a dynamic input range of 0.2 × 20.48 V or 4.096 V. The center point of this range is set by the 1.707 V reference voltage. With the reference set to 1.707 V, the center point is at 0 V and the input voltage can range from -10.24 V to +10.24 V. To maintain the best accuracy, the input range should be limited to -10.0 V to +10.0 V.
The A/D converter inputs are factory-calibrated and the calibration constants are stored in flash memory. You may calibrate the A/D converter inputs at a later time using the software functions described in Section 4.3.4, "A/D Converter Inputs." The GETCALIB.C and the SAVECALIB.C sample programs in the Dynamic C SAMPLES\BL2100\ Calib_Save_Retrieve folder illustrate how to retrieve and save calibration data.
3.5 D/A Converter Outputs
Only the BL2100 and the BL2120 models are stuffed with D/A converters. The D/A converter outputs are buffered and scaled to provide an output from 0 V to +10 V.
NOTE The D/A converter output voltage depends on the original power-supply voltage, +RAW, so if +RAW < 13 V, the maximum D/A converter output will be +RAW - 3 V. Figure 17 shows the D/A converter outputs.
To stay within the maximum power dissipation of the D/A converter circuit, the maximum D/A converter output current is 10 mA per channel for a power-supply voltage, +RAW, up to 15 V, and drops to 2 mA per channel for a power-supply voltage of 36 V.
The D/A converter inputs are factory-calibrated and the calibration constants are stored in flash memory. You may calibrate the A/D converter inputs at a later time using the software functions described in Section 4.3.5, "D/A Converter Outputs." The GETCALIB.C and the SAVECALIB.C sample programs in the Dynamic C SAMPLES\BL2100\ Calib_Save_Retrieve folder illustrate how to retrieve and save calibration data.
3.6 Analog Reference Voltage Circuit
Figure 19 shows the analog voltage reference circuit.
This circuit generates the 4.096 V reference voltage, which is used by the A/D converter and by the D/A converters. This sets the operating range of the A/D converter and the D/A converters (0-10 V). To use the full accuracy of the A/D converter and the D/A converters, this voltage must be accurate to the same degree.
The reference zener diode in combination with the 300 W resistor form a shunt regulator. The 4.096 V reference voltage then feeds the A/D converter, the D/A converters, and the voltage divider composed of the 10 kW and the 14 kW resistors. The voltage divider generates a second reference voltage of 1.707 V to feed the four op-amps for the buffered A/D converter inputs.
The 2.048 V reference voltage is also used to generate the 2.5 V reference for D-REF used in the digital output circuit.
3.7 Memory
3.7.1 SRAM
The BL2100 module is designed to accept 128K to 512K of SRAM packaged in an SOIC case. The standard BL2100 modules come with 128K of SRAM.
3.7.2 Flash Memory
The BL2100 is also designed to accept 128K to 512K of flash memory packaged in a TSOP case. The standard BL2100 modules comes with one 256K flash memory.
NOTE Z-World recommends that any customer applications should not be constrained by the sector size of the flash memory since it may be necessary to change the sector size in the future. A Flash Memory Bank Select jumper configuration option based on 0 W surface-mounted resistors exists at header JP2 on the RabbitCore module. This option, used in conjunction with some configuration macros, allows Dynamic C to compile two different co-resident programs for the upper and lower halves of the 256K flash in such a way that both programs start at logical address 0000. This is useful for applications that require a resident download manager and a separate downloaded program. See Application Note 218, Implementing a Serial Download Manager for a 256K Flash, for details.
3.8 External Interrupts
The BL2100 is already configured to support external interrupts on pin 11 of screw terminal header J11. The external interrupt circuit is shown in Figure 20.
In addition to its primary use as an external interrupt, pin 11 of screw terminal header J11 may also be used as a CMOS-level digital input or output, or to generate a PWM signal.
When using pin 11 as a CMOS-level digital input or output, use the standard Rabbit 2000 register function configuration for PE5 (on Parallel Port E) to set this pin up for your intended use. Be aware that there is no provision for protection against voltage spikes while PE5 is pulled up to Vcc with a 27 kW pull-up resistor.
The sample program PWM.C in the Dynamic C SAMPLES/BL2100 directory illustrates how to use pin 11 of screw terminal header J11 to generate a PWM signal.
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