Rabbit RabbitCore RCM3209, User Manual, Page: 30 / 160

24 RabbitCore RCM3209/RCM3229
Notes
1. When using pins 33–34 on header J61 to drive LEDs, you must use an external buffer
to drive these external LEDs. These pins are not connected on the RCM3229, which
does not have the LEDs installed.
2. The VRAM voltage is temperature-dependent. If the VRAM voltage drops below about
1.2 V to 1.5 V, the contents of the battery-backed SRAM may be lost. If VRAM drops
below 1.0 V, the 32 kHz oscillator could stop running. Pay careful attention to this volt-
age if you draw any current from this pin.
Header
J
6
2
20 PG7 Input/Output RXE
Serial Port E
21 PG6 Input/Output TXE
22 PG5 Input/Output RCLKE Serial Clock E input
23 PG4 Input/Output TCLKE Serial Clock E ouput
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 See
Notes
below table
30 VBAT_EXT 3 V battery Input
Minimum battery
voltage 2.85 V
31 +3.3V Input 3.15–3.45 V DC
32 GND
33 n.c. Reserved for future use
34 GND
Table 2. RCM3209/RCM3229 Pinout Configurations (continued)
Pin Pin Name Default Use Alternate Use Notes