External Memory Interface
When necessary the AT90USB1287's 8k Bytes of internal SRAM can be extended through the AVR external memory interface. The suggested external SRAM is 32k Bytes and is available from address 0x8000 to 0xFFFF giving a total of 40k Bytes when assembled.
Suggested latch and RAM:
-
74AHC573PW.
-
BS62UV256TCP-10.
Serial Interface
The USART on the AT90USB1287 is routed to J4 on the RZRAVEN's backside. J4 is implemented as three large pads (RX-TX-GND) where the user can solder in wires and route the signal to his or her preference. The RX-TX signals are TTL level, so an external level converter must be connected if RS232 levels are necessary.
Programming Interface
A JTAG interface is provided for the AT90USB1287 microcontroller. The interface is available through a 50-mil spaced 10-pin dual row header. The RZRAVEN does not come with the header mounted. So it is up to the user populating it. Wires could also be soldered in instead of the dual row headers. A total of 5 50-mil pin headers and one 50-mil to 100-mil converter are supplied with the RZRAVEN kit.
LEDs
4 LEDs are assembled on the board:
| LED | AT90USB1287 port pin | Comment |
|---|---|---|
| Blue (D1) | PORTD7 | Turn LED on by pulling port pin high |
| Red (D2) | PORTD5 | Turn LED on by pulling port pin low |
| Green (D3) | PORTE7 | Turn LED on by pulling port pin low |
| Orange (D4) | PORTE6 | Turn LED on by pulling port pin low |