101-1109 Rabbit Semiconductor, 101-1109 Datasheet - Page 44

• Manufacturer Part Number: 101-1109
• Description: KIT EMBEDDED PLC APPLICATION
• Manufacturer: Rabbit Semiconductor
• Series: Coyoter
• Type: MPU Moduler

Specifications of 101-1109

• Contents: BL2500, ISaGRAF V3.50, Embedded PLC software kernel, ISaGRAF Programming Cable and Documentation
• For Use With/related Products: BL2500
• Lead Free Status / RoHS Status: Vendor undefined / Vendor undefined

EMBEDDED
the gain resistors in the circuit have a 1% tolerance. The D/A converters therefore need individual
calibration, with the calibration constants held in software before absolute accuracy can be relied on. The
BL2500 has such calibration.
Pulse-width modulation (PWM) is used for the D/A conversion. The digital signal, which is either 0 V or
3.3 V, will be a train of pulses. This means that if the signal is taken to be usually at 0 V (or ground), the
pulses will be some 3.3 V pulses of varying width. The voltage will be 0 V for a given time, then jump to
3.3 V for a given time, then back to ground for a given time, then back to 3.3 V, and so on. A hardware
filter that consists of a resistor and capacitor averages the 3.3 V signal and the 0 V signal over time.
Therefore, if the time that the signal is at 3.3 V is equal to the time the signal is 0 V, the duty cycle will be
50%, and the average signal will be 1.65 V. If the time at 3.3 V is only 25% of the time, then the average
voltage will be 0.825 V. Thus, the software needs to only vary the time the signal is at 3.3 V with respect
to the time the signal is at 0 V to achieve any desired voltage between 0 and 3.3 V. It is very easy to do
pulse-width modulation with the Rabbit 3000 microprocessor because the chip's architecture includes an
advanced PWM feature.
4.5 COMMUNICATION INTERFACES
4.5.1 Serial Ports
The BL2500 can be configured (using
the RS485 (serial port D). The serial port chosen will be used as the communication channel with either
the ISaGRAF Workbench or a Modbus master. The serial port A is used by the programming cable.
4.5.1.1 RS-232
The BL2500 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 3000's CMOS/TTL signals to RS-232
signal levels. Note that the polarity is reversed in an RS-232 circuit so that a +3.3 V output becomes
approximately -6 V and 0 V is output as +6 V. The RS-232 transceiver also provides the proper line
loading for reliable communication.
RS-232 can be used effectively for distances of up to 15 m.
4.5.1.2 RS-485
The BL2500 has one RS-485 serial channel, which is connected to the Rabbit 3000 Serial Port D through
an RS-485 transceiver. The half-duplex communication uses PA4 to control the transmit enable on the
communication line. Using this scheme a strict master/slave relationship must exist between devices to
insure that no two devices attempt to drive the bus simultaneously.
The BL2500 can be used in an RS-485 multidrop network spanning up to 1200 m (4000 ft), and there can
be as many as 32 attached devices. Connect the 485+ to 485+ and 485- to 485- using single twisted-pair
wires as shown in Figure 9. Note that a common ground is recommended.
OEM Technology Solutions
PLC BL2500 User’s Manual
Serial Port
D
Table 2:
A
E
EMBEDDED
Programming Port
RS-485 (3-wires)
RS-232 (3-wires)
EMBEDDED
Use
PLC BL2500 Serial Port Configuration
PLC Utility) to use either one RS-232 (serial port E) or
J3 (Rabbit core module)
Header
J9
J6
Hardware Reference
Page 38