| MiniCom (OP6800) User's Manual |
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3. Subsystems
Chapter 3 describes the principal subsystems for the OP6800.
- · Digital I/O
- · Serial Communication
- · Memory
Figure 6 shows these Rabbit-based subsystems designed into the OP6800.
3.1 Pinouts
Figure 7 shows the OP6800 pinouts.
Header J1 is a standard 2 × 20 header with a nominal 0.1" pitch. The OP6800 also has an RJ-45 Ethernet jack on the RabbitCore module.
3.2 Digital I/O
3.2.1 Digital Inputs
The OP6800 has eight digital inputs, IN00-IN07, each with a current-limiting resistor of 27 kW, and protected over a range of -36 V to +36 V. The inputs are all pulled up to +5 V as shown in Figure 8.
The OP6800 also has five digital inputs, IN08-IN12, each with a current-limiting resistor of 12 kW, protected over a range of -25 V to +25 V, and pulled up to +5 V.
The actual switching threshold for IN00-IN12 is approximately 2.40 V. Anything below this value is a logic 0, and anything above is a logic 1.
IN13-IN17 are connected in parallel with five of the keypad buttons. These inputs are normally pulled up, but pulling one of these inputs down is the equivalent of pressing the corresponding keypad key remotely.
Table 2. Remote Keypad Operation 0 ( )
IN13 1 ( )
IN14 2 ( )
IN15 3 ( )
IN16 6 ( )
IN17 3.2.2 Digital Outputs
The OP6800 has 11 digital outputs, OUT00-OUT10, which can each sink up to 200 mA. Figure 9 shows a wiring diagram for using the digital outputs.
OUT00-OUT06 can switch up to 40 V and the corresponding LEDs when the outputs are on. OUT07-OUT10 offer protection for inductive loads when K is connected to an external power supply; OUT07-OUT10 are not connected to the LEDs.
It is possible to use an external open-collector driver to control the LEDs associated with OUT00-OUT06. Connect the external driver to the output corresponding to the LED you wish to control, but keep the internal driver turned off. The external driver will then control the LED.
3.3 Serial Communication
The OP6800 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 3 summarizes the options.
Table 3. Serial Communication Configurations 0 RS-232, 3-wire RS-232, 3-wire RS-485 1 RS-232, 5-wire CTS/RTS RS-485 The OP6800 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 OP6800 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 OP6800 uses an 11.0592 MHz crystal, which is doubled to 22.1184 MHz. At this frequency, the OP6800 supports standard asynchronous baud rates up to a maximum of 230,400 bps.
3.3.1 RS-232
The OP6800 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 OP6800's maximum baud rate for distances of up to 15 m.
3.3.2 RS-485
The OP6800 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 OP6800 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 10. Note that a common ground is recommended.
The OP6800 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 11.
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 OP6800 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 OP6800. 3.3.3 Programming Port
The RabbitCore module on the OP6800 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 OP6800 in a mode where the OP6800 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 OP6800 to start up in an external bootstrap mode. The OP6800 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 (OP6800 models only)
Figure 12 shows the pinout for the Ethernet port (J2 on the OP6800 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 12) 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 12.
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 13.
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 Memory
3.4.1 SRAM
The OP6800 module is designed to accept 128K to 512K of SRAM packaged in an SOIC case. The standard OP6800 modules come with 128K of SRAM.
3.4.2 Flash Memory
The OP6800 is also designed to accept 128K to 512K of flash memory. The standard OP6800 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.
3.5 Keypad Labeling
The keypad may be labeled according to your needs. A template is provided in Figure 14 to allow you to design your own keypad label insert.
Before you can replace the keypad legend, you will have to remove the LCD/keypad module from the plastic bezel. The LCD/keypad module circuit board is held down with two screws and two tabs as shown in Figure 15.
To replace the keypad legend, remove the old legend and insert your new legend prepared according to the template in Figure 14. The keypad legend is located under the blue keypad matte, and is accessible from either the left side or the right side as shown in Figure 16. A small screwdriver or a similar small pointed objectcan be used to nudge the keypad legend in or out.
Once you have replaced the keypad label, re-insert the LCD/keypad module circuit board under the mounting tabs in the plastic bezel, as shown in Figure 15. Secure the LCD/keypad module circuit board with the two screws.
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