> ## Appendix C. Subsystems

> Appendix D describes the principal subsystems for the RabbitLink.

> - RabbitLink Subsystems
> - Serial Communication
> - Memory
> - Power Supplies

> ### C.1 RabbitLink Hardware Subsystems

> Figure D-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 D-1. RabbitLink Subsystems

> #### C.1.1 Pinouts

> Figure D-2 shows the pinouts for the RJ-45 Ethernet jack and the two programming headers on the RabbitLink board.

> Figure D-2. Pinouts for Ethernet Jack and Programming Headers

> ### C.2 Serial Communication

> #### C.2.1 Serial Programming Ports

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

> NOTE | Refer to the`Rabbit 2000 Microprocessor User's Manual` for more information related to the bootstrap mode.

> The `PROG IN` port is used with the `DIAG` connector on the programming cable to configure the RabbitLink. The `PROG IN` port transmits information to and from a PC running a terminal emulation program.

> The RabbitLink network configuration can be reset through the `PROG IN` port.

> The `PROG OUT` port is used (with the `PROG` connector on the program download cable connected to the programming port of the target) to download or to debug a program through an Ethernet-based network or even the Internet to a target Rabbit-based board. The `PROG OUT` port transmits information to and from a PC elsewhere on the Ethernet-based network running Dynamic C Premier (version 7.02 or later) or the Rabbit Field Utility.

> NOTE | See Appendix D, "Programming Cable," for more information.

> #### 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 that may already be installed, 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, which are terminated in an eight-pin (RJ-45 style) connector. This means that four pins of the eight-pin MDI connector are used as shown in Figure D-2. 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

> #### C.3.1 SRAM

> The RabbitLink is designed to accept 128K or 512K of SRAM packaged in an SOIC case.

> The standard models sold by Z-World and by Rabbit Semiconductor come with 128K of SRAM. Figure D-3 shows the locations and the jumper settings for the jumpers at JP4 used to set the SRAM size. The "jumpers" are 0 `W` surface-mounted resistors.

> Figure D-3. RabbitLink Jumper Settings
> for SRAM and Flash EPROM Size

> #### 3.3.2 Flash EPROM

> The RabbitLink is also designed to accept 128K to 512K of flash memory packaged in a TSOP case.

> The RabbitLink comes with two 256K flash memories, one for the firmware and one for data. Figure D-3 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.

> #### 3.3.3 Dynamic C Premier BIOS Source Files

> The Dynamic C Premier BIOS source files handle different standard RAM and flash memory sizes automatically.

> ### 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/J6. The connection through jack J4 is protected against reverse polarity by a Sshottky diode at D1 as shown in Figure D-4, but the alternative connection through J5/J6 is `not` protected against reverse polarity.

> Figure D-4. 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/J6 enables you to connect the RabbitLink directly to a power supply in the production system.

> Capacitor C8 provides noise and ripple stablization 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 or DCIN input voltage may range from 9 V to 40 V.

> ### C.5 Batteries and External Battery Connections

> Although the RabbitLink has room for a backup battery on the circuit board, battery backup is not supported at this time.

> ### C.6 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.

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