<< Previous | Index | Next >>

Appendix C. Subsystems

This appendix describes the principal subsystems for the RabbitLink.

• Serial Communication
• Memory
• Power Supplies
• Reset Generator

C.1 RabbitLink Hardware Subsystems

Figure C.1.0-1 shows the Rabbit-based subsystems designed into the RabbitLink and shows the parallel ports and signal lines they use on the Rabbit 2000 microprocessor.

Figure C.1.0-1 RabbitLink Subsystems

NOTE	PB0 is an output by default, but can be an input by removing jumper R58 and adding jumpers R59 and R60.

C.1.1 Pinouts

Figure C.1.1-1 shows the pinouts for the RJ-45 Ethernet jack and the two programming headers on the RabbitLink board.

Figure C.1.1-1 Pinouts for Ethernet Jack and Programming Headers

C.2 Serial Communication

The RabbitLink uses 2 serial ports of the Rabbit 2000 microprocessor.

C.2.1 Serial Programming Ports

The RabbitLink board has two 10-pin programming headers labeled J8 and J9. The PROG IN (J8) header uses the Rabbit 2000's serial port A for communication, and PROG OUT (J9) uses serial port B. The Rabbit 2000 startup-mode pins (SMODE0, SMODE1) are presented to PROG IN so that an externally connected device can force a start-up in an external bootstrap mode when the PROG connector on the programming cable is used.

NOTE	Refer to the Rabbit 2000 Microprocessor User's Manual for more information on the bootstrap mode.

The PROG IN header is used with the DIAG connector on the programming cable to configure network addresses for the RabbitLink. This connection transmits information to and from a PC running a terminal emulation program. The PROG IN header is also used with the PROG connector on the programming cable. With this connection, you can download firmware to the RabbitLink and also reset default network addresses.

The PROG OUT header is connected with the program download cable to the programming port of the Rabbit-based target. This connection allows the RabbitLink to transmit information to and from the Rabbit-based target. A network-enabled PC running Dynamic C or the RFU communicates with the RabbitLink using the RabbitLink's Ethernet connection. These 2 connections give you the power to remotely download and/or debug an application on a Rabbit-based target.

C.2.2 Ethernet Port

The 10 Mbps twisted-pair Ethernet system allows segment lengths of approximately 100 m for voice-grade twisted-pair telephone wiring. The maximum segment length may be shorter or longer than this, depending on the quality of the twisted-pair cabling in your system. While the 10Base-T system is designed to use voice-grade telephone cable, higher quality Category 5 cables, connectors, and wire terminating devices provide the best possible signal carrying system for 100 Mbps Ethernet media systems.

The 10Base-T media system uses two pairs of wires. They are terminated in an 8-pin (RJ-45 style) connector. Four pins of the 8-pin connector are used as shown in Figure C.1.1-1. The transmit and receive data signals on each pair of a 10Base-T segment are polarized, with one wire of each signal pair carrying the positive (+) signal, and the other carrying the negative (-) signal.

C.3 Memory

The RabbitLink has SRAM and flash memory devices. The Dynamic C BIOS handles different standard RAM and flash memory sizes automatically.

C.3.1 SRAM

The RabbitLink is designed to accept 128K or 512K of SRAM packaged in an SOIC case. It comes standard with 128K of SRAM. Figure C.3.1-1 shows the locations and the jumper settings for the jumpers at JP4 used to set the SRAM size. The jumpers are 0 W surface-mount resistors.

Figure C.3.1-1 RabbitLink Jumper Settings for SRAM and Flash EPROM Size

C.3.2 Flash EPROM

The RabbitLink is designed to accept 128K to 512K of flash memory packaged in a TSOP case. It comes with two 256K flash memories, one for the firmware and one for data. Figure C.3.1-1 shows the locations and the jumper settings for the jumpers at JP2 and JP3 used to set the flash memory size. The "jumpers" are 0 W surface-mounted resistors.

NOTE	Z-World recommends that any customer applications should not be constrained by the sector size of the flash EPROM since it may be necessary to change the sector size in the future.

C.4 Power Supplies

Power is supplied to the RabbitLink board from an external source either through jack J4 or through screw terminal connector J5. The connection through jack J4 is protected against reverse polarity by a Schottky diode at D1 as shown in Figure C.4.0-1.

Figure C.4.0-1 RabbitLink Power Supply Schematic

The power supply connection through jack J4 is handy for the AC adapter included with the RabbitLink tool kit for desktop demonstration and development. The power supply connection through screw terminal connector J5 enables you to connect the RabbitLink directly to a power supply in the production system.

Capacitor C8 provides noise and ripple stabilization protection for the voltage regulator, and allows the external power supply to be located some distance away from the RabbitLink. A switching power regulator is used. The +RAW input voltage may range from 9 V to 40 V.

C.5 Reset Generator

The RabbitLink uses a reset generator, U14, to reset the Rabbit 2000 microprocessor when the voltage drops below the voltage necessary for reliable operation. The reset occurs between 4.50 V and 4.75 V, typically 4.63 V.