RabbitCore RCM3000 User's Manual

4. Hardware Reference

Chapter 3 describes the hardware components and principal hardware subsystems of the RCM3000. Appendix A, "RCM3000 Specifications," provides complete physical and electrical specifications.

Figure 4 shows these Rabbit-based subsystems designed into the RCM3000.

Figure 4. RCM3000 Subsystems

4.1 RCM3000 Digital Inputs and Outputs

The RCM3000 has 52 parallel I/O lines grouped in seven 8-bit ports available on headers J1 and J2. The 44 bidirectional I/O lines are located on pins PA0–PA7, PB0, PB2–PB7, PD2–PD7, PE0–PE1, PE3–PE7, PF0–PF7, and PG0–PG7.

Figure 5 shows the RCM3000 pinouts for headers J1 and J2.

Figure 5. RCM3000 Pinouts

Headers J1 and J2 are standard 2 × 34 headers with a nominal 2 mm pitch. An RJ-45 Ethernet jack is also included with the RCM3000.

The signals labeled PD2, PD3, PD6, and PD7 on header J1 (pins 29–32) and the pins that are not connected (pins 33–34 on header J1 and pin 33 on header J2) are reserved for future use on other models in the RCM3000.

Figure 6 shows the use of the Rabbit 3000 ports in the RCM3000 modules.

Figure 6. Use of Rabbit 3000 Ports

The ports on the Rabbit 3000 microprocessor used in the RCM3000 are configurable, and so the factory defaults can be reconfigured. Table 2 lists the Rabbit 3000 factory defaults and the alternate configurations.

Table 2. RCM3000 Pinout Configurations 

Pin		Pin Name	Default Use	Alternate Use	RCM3000 Use
Header J1	1	GND
	2	STATUS	Output (Status)	Output
	3–10	PA[7:0]	Parallel I/O	External data bus (ID0–ID7) Slave port data bus (SD0–SD7)	External Data Bus
	11	PF3	Input/Output	QD2A
	12	PF2	Input/Output	QD2B
	13	PF1	Input/Output	QD1A CLKC
	14	PF0	Input/Output	QD1B CLKD
	15	PC0	Output	TXD
	16	PC1	Input	RXD
	17	PC2	Output	TXC
	18	PC3	Input	RXC
	19	PC4	Output	TXB
	20	PC5	Input	RXB
	21	PC6	Output	TXA	Serial Port A (programming port)
	22	PC7	Input	RXA
	23	PG0	Input/Output	TCLKF
	24	PG1	Input/Output	RCLKF
	25	PG2	Input/Output	TXF
	26	PG3	Input/Output	RXF
	27	PD4	Input/Output	ATXB
	28	PD5	Input/Output	ARXB
	29	PD2	Input/Output	TPOUT– *	Ethernet transmit port
	30	PD3	Input/Output	TPOUT+ *
	31	PD6	Input/Output	TPIN– *	Ethernet receive port
	32	PD7	Input/Output	TPIN+ *
	33–34 *	n.c.			Not connected
* Pins 29–34 are reserved for future RCM3000 RabbitCore modules.
Header J2	1	/RES	Reset output	Reset input	Reset output from Reset Generator
	2	PB0	Input/Output	CLKB
	3	PB2	Input/Output	IA0 /SWR	External Address 0
	4	PB3	Input/Output	IA1 /SRD	External Address 1
	5	PB4	Input/Output	IA2 SA0	External Address 2
	6	PB5	Input/Output	IA3 SA1	External Address 3
	7	PB6	Input/Output	IA4	External Address 4
	8	PB7	Input/Output	IA5 /SLAVEATTN	External Address 5
	9	PF4	Input/Output	AQD1B PWM0
	10	PF5	Input/Output	AQD1A PWM1
	11	PF6	Input/Output	AQD2B PWM2
	12	PF7	Input/Output	AQD2A PWM3
	13	PE7	Input/Output	I7 /SCS
	14	PE6	Input/Output	I6
	15	PE5	Input/Output	I5 INT1B
	16	PE4	Input/Output	I4 INT0B
	17	PE3	Input/Output	I3
	18	PE1	Input/Output	I1 INT1A
	19	PE0	Input/Output	I0 INT0A
Header J2	20	PG7	Input/Output	RXE
	21	PG6	Input/Output	TXE
	22	PG5	Input/Output	RCLKE
	23	PG4	Input/Output	TCLKE
	24	/IOWR	Output		External write strobe
	25	/IORD	Input		External read strobe
	26–27	SMODE0, SMODE1	(0,0)—start executing at address zero (0,1)—cold boot from slave port (1,0)—cold boot from clocked Serial Port A SMODE0 =1, SMODE1 = 1 Cold boot from asynchronous Serial Port A at 2400 bps (programming cable connected)		Also connected to programming cable
	28	/RESET_IN	Input		Input to Reset Generator
	29	VRAM	Output		Maximum Current Draw 15 µA
	30	VBAT_EXT	3 V battery Input		Minimum battery voltage 2.8 V
	31	+3.3V	Input		3.15–3.45 V DC
	32	GND
	33	n.c.			Future option for +5 V input or +5 V output
	34	GND

NOTE	Ports PD0 and PE2 are used for the Ethernet interface.

Locations R38–R43 allow the population of 0 W resistors (jumpers) that will be used to enable future options. These locations are currently unused.

4.1.1 Memory I/O Interface

The Rabbit 3000 address lines (A0–A19) and all the data lines (D0–D7) are routed internally to the onboard flash memory and SRAM chips. I/0 write (/IOWR) and I/0 read (/IORD) are available for interfacing to external devices.

Parallel Port A can also be used as an external I/O data bus to isolate external I/O from the main data bus. Parallel Port B pins PB2–PB7 can also be used as an external address bus.

When using the auxiliary I/O bus, you must add the following line at the beginning of your program.

#define PORTA_AUX_IO    // required to enable auxiliary I/O bus

The STATUS output has three different programmable functions:

5. It can be driven low on the first op code fetch cycle.

6. It can be driven low during an interrupt acknowledge cycle.

7. It can also serve as a general-purpose output.

4.1.2 Other Inputs and Outputs

Two status mode pins, SMODE0 and SMODE1, are available as inputs. The logic state of these two pins determines the startup procedure after a reset.

/RESET_IN is an external input used to reset the Rabbit 3000 microprocessor and the RabbitCore RCM3000 memory. /RES is an output from the reset circuitry that can be used to reset other peripheral devices.

4.1.3 5 V Tolerant Inputs

The RCM3000 operates over a voltage from 3.15 V to 3.45 V, but most RCM3000 input pins, except /RESET_IN, VRAM, VBAT_EXT, and the power-supply pins, are 5 V tolerant. When a 5 V signal is applied to 5 V tolerant pins, they present a high impedance even if the Rabbit power is off. The 5 V tolerant feature allows 5 V devices that have a suitable switching threshold to be connected directly to the RCM3000. This includes HCT family parts operated at 5 V that have an input threshold between 0.8 and 2 V.

NOTE

CMOS devices operated at 5 V that have a threshold at 2.5 V are not suitable for direct connection because the Rabbit 3000 outputs do not rise above VDD, and is often specified as 3.3 V. Although a CMOS input with a 2.5 V threshold may switch at 3.3 V, it will consume excessive current and switch slowly.

In order to translate between 5 V and 3.3 V, HCT family parts powered from 5 V can be used, and are often the best solution. There is also the "LVT" family of parts that operate from 2.0 V to 3.3 V, but that have 5 V tolerant inputs and are available from many suppliers. True level-translating parts are available with separate 3.3 V and 5 V supply pins, but these parts are not usually needed, and have design traps involving power sequencing.

4.2 Serial Communication

The RCM3000 board does not have an RS-232 or an RS-485 transceiver directly on the board. However, an RS-232 or RS-485 interface may be incorporated on the board the RCM3000 is mounted on. For example, the Prototyping Board has a standard RS-232 transceiver chip.

4.2.1 Serial Ports

There are six serial ports designated as Serial Ports A, B, C, D, E, and F. All six serial ports can operate in an asynchronous mode up to the baud rate of the system clock divided by 16. 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 Ports A, B, C, and D can also be operated 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. When the Rabbit 3000 provides the clock, the baud rate can be up to 80% of the system clock frequency divided by 128, or 183,750 bps for a 29.4 MHz clock speed.

Serial Ports E and F can also be configured as SDLC/HDLC serial ports. The IRDA protocol is also supported in SDLC format by these two ports.

Serial Port A is available only on the programming port.

4.2.2 Ethernet Port

Figure 7 shows the pinout for the RJ-45 Ethernet port (J4). Note that some Ethernet connectors are numbered in reverse to the order used here. 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 Ethernet signals are also available on header J1.

Figure 7. RJ-45 Ethernet Port Pinout

The transformer/connector assembly ground is connected to the RCM3000 printed circuit board digital ground via a 0 W resistor, R31, as shown in Figure 8. The RJ-45 connector is shielded to minimize EMI effects to/from the Ethernet signals.

Figure 8. Isolation Resistor R31

4.2.3 Serial Programming Port

The RCM3000 serial programming port is accessed using header J3 or over an Ethernet connection via the RabbitLink EG2110. The programming port uses the Rabbit 3000's Serial Port A for communication. Dynamic C uses the programming port to download and debug programs.

The programming port is also used for the following operations.

• Cold-boot the Rabbit 3000 on the RCM3000 after a reset.

• Remotely download and debug a program over an Ethernet connection using the RabbitLink EG2110.

• Fast copy designated portions of flash memory from one Rabbit-based board (the master) to another (the slave) using the Rabbit Cloning Board.

Programming may also be initiated through the motherboard to which the RCM3000 series module is plugged in to since the Serial Port A (PC6 and PC7), SMODE0, SMODE1, and /RESET_IN are available on headers J1 and J2 (see Table 2).

Alternate Uses of the Serial Programming Port

All three clocked Serial Port A signals are available as

• a synchronous serial port

• an asynchronous serial port, with the clock line usable as a general CMOS input

The serial programming port may also be used as a serial port via the DIAG connector on the serial programming cable.

In addition to Serial Port A, the Rabbit 3000 startup-mode (SMODE0, SMODE1), status, and reset pins are available on the serial programming port.

The two startup-mode pins determine what happens after a reset—the Rabbit 3000 is either cold-booted or the program begins executing at address 0x0000.

The status pin is used by Dynamic C to determine whether a Rabbit microprocessor is present. The status output has three different programmable functions:

1. It can be driven low on the first op code fetch cycle.

2. It can be driven low during an interrupt acknowledge cycle.

3. It can also serve as a general-purpose CMOS output.

The /RESET_IN pin is an external input that is used to reset the Rabbit 3000 and the RCM3000 onboard peripheral circuits. The serial programming port can be used to force a hard reset on the RCM3000 by asserting the /RESET_IN signal.

Refer to the Rabbit 3000 Microprocessor User's Manual for more information.

4.3 Serial Programming Cable

The programming cable is used to connect the serial programming port of the RCM3000 to a PC serial COM port. The programming cable converts the RS-232 voltage levels used by the PC serial port to the CMOS voltage levels used by the Rabbit 3000.

When the PROG connector on the programming cable is connected to the RCM3000 serial programming port at header J3, programs can be downloaded and debugged over the serial interface.

The DIAG connector of the programming cable may be used on header J3 of the RCM3000 with the RCM3000 operating in the Run Mode. This allows the programming port to be used as a regular serial port.

4.3.1 Changing Between Program Mode and Run Mode

The RCM3000 is automatically in Program Mode when the PROG connector on the programming cable is attached, and is automatically in Run Mode when no programming cable is attached. When the Rabbit 3000 is reset, the operating mode is determined by the status of the SMODE pins. When the programming cable's PROG connector is attached, the SMODE pins are pulled high, placing the Rabbit 3000 in the Program Mode. When the programming cable's PROG connector is not attached, the SMODE pins are pulled low, causing the Rabbit 3000 to operate in the Run Mode.

Figure 9. Switching Between Program Mode and Run Mode

A program "runs" in either mode, but can only be downloaded and debugged when the RCM3000 is in the Program Mode.

Refer to the Rabbit 3000 Microprocessor User's Manual for more information on the programming port and the programming cable.

4.3.2 Standalone Operation of the RCM3000

The RCM3000 must be programmed via the Prototyping Board or via a similar arrangement on a customer-supplied board. Once the RCM3000 has been programmed successfully, remove the serial programming cable from the programming connector and reset the RCM3000. The RCM3000 may be reset by cycling the power off/on or by pressing the RESET button on the Prototyping Board. The RCM3000 module may now be removed from the Prototyping Board for end-use installation.

CAUTION: Disconnect power to the Prototyping Board or other boards when removing or installing your RCM3000 module to protect against inadvertent shorts across the pins or damage to the RCM3000 if the pins are not plugged in correctly. Do not reapply power until you have verified that the RCM3000 module is plugged in correctly.

4.4 Other Hardware

4.4.1 Clock Doubler

The RCM3000 takes advantage of the Rabbit 3000 microprocessor's internal clock doubler. A built-in clock doubler allows half-frequency crystals to be used to reduce radiated emissions. The 29.4 MHz frequency specified for the RCM3000 is generated using a 14.7456 MHz crystal. The clock doubler will not work for crystals with a frequency above 26.7264 MHz.

The clock doubler may be disabled if 29.4 MHz clock speeds are not required. Disabling the Rabbit 3000 microprocessor's internal clock doubler will reduce power consumption and further reduce radiated emissions. The clock doubler is disabled with a simple global macro as shown below.

Select the "Defines" tab from the Dynamic C Options > Project Options menu. Add the line CLOCK_DOUBLED=0 to always disable the clock doubler. The clock doubler is enabled by default, and usually no entry is needed. If you need to specify that the clock doubler is always enabled, add the line CLOCK_DOUBLED=1 to always enable the clock doubler. Click OK to save the macro. The clock doubler will now remain off whenever you are in the project file where you defined the macro.

4.4.2 Spectrum Spreader

The Rabbit 3000 features a spectrum spreader, which helps to mitigate EMI problems. By default, the spectrum spreader is on automatically, but it may also be turned off or set to a stronger setting. The means for doing so is through a simple global macro as shown below.

Select the "Defines" tab from the Dynamic C Options > Project Options menu. Normal spreading is the default, and usually no entry is needed. If you need to specify normal spreading, add the line ENABLE_SPREADER=1 For strong spreading, add the line ENABLE_SPREADER=2 To disable the spectrum spreader, add the line ENABLE_SPREADER=0 NOTE The strong spectrum-spreading setting is not recommended since it may limit the maximum clock speed or the maximum baud rate. It is unlikely that the strong setting will be used in a real application. Click OK to save the macro. The spectrum spreader will now remain off whenever you are in the project file where you defined the macro.

NOTE	Refer to the Rabbit 3000 Microprocessor User's Manual for more information on the spectrum-spreading setting and the maximum clock speed.

4.5 Memory

4.5.1 SRAM

The RCM3000 can accept 128K to 512K of SRAM at U4.

4.5.2 Flash EPROM

The RCM3000 can accept 256K to 512K of flash EPROM.

NOTE	Rabbit Semiconductor 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.

Writing to arbitrary flash memory addresses at run time is also discouraged. Instead, define a "user block" area to store persistent data. The functions writeUserBlock and readUserBlock are provided for this.

A Flash Memory Bank Select jumper configuration option based on 0 W surface-mounted resistors exists at header JP1 on the RCM3000 RabbitCore modules. 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 Technical Note 218, Implementing a Serial Download Manager for a 256K Flash, for details.

4.5.3 Dynamic C BIOS Source Files

The Dynamic C BIOS source files handle different standard RAM and flash EPROM sizes automatically.