Applied Data Systems Bitsy Plus, User Manual, Page: 29 / 68

Feature Reference
ADS document # 110114-1001A Page 19
GP Signal Name I/O
11
Function, Connector
14 CTS1 I
15 RTS1 O
16 RIB1 I
17 DCD1 I
Serial 1 (J10, 4.5.1)
18 CTS3 I
19 RTS3 O
Serial 3 (J3, 4.5.1)
20 LED0/DTR1 O LED0 or Serial 1 (J10)
21
GPIO21_MBGNT
O SA-1111 Memory Request Bus Grant
22
GPIO22_MBREQ
I SA-1111 Memory Bus Request
23 /IRDAON O IRDA enable (J3)
24 DSR1 I Serial 1 (J3)
25 /RESET_AVR O Reset ADSmartIO
26 /SA1111_RESET O Reset SA-1111
27 GPIO27_CLK O System clock for use by SA-1111
4.2 Real-Time Clock (RTC)
The Bitsy Plus uses the DS1307 real-time clock chip to maintain the system date and time when
the system is powered down. The operating system typically reads the RTC on boot and wakeup,
and sets the RTC when the system time or date is changed.
The RTC is powered from the BATPOS input. Connect a long-life 3 V battery to the BATPOS
input (J3 pin 50) to maintain the system time.
The RTC is accessible through the ADSmartIO's I
2
C bus (section 4.5.4). See section 6.2.4 for
electrical specifications.
4.3 ADSmartIO
ADSmartIO
TM
is a RISC microcontroller on the Bitsy Plus that is programmed with ADS
firmware. This device provides additional I/O functionality for specialized tasks. Your
application software can configure the standard ADSmartIO for a variety of functions, such as
digital I/O, PWM, A/D, I
2
C, keypad scan and PS/2 keyboard operation.
4.3.1 Overview
The ADSmartIO controller has four, eight-pin I/O ports named PA, PB, PC and PD. Some of
these ports' pins are used internally, while others are available for user applications. See the signal
cross-reference in section 4.3.7 for details.
Generally, ADSmartIO ports are referenced by port and pin number (e.g. PA2), but I/O signals
may go by several names based on its functionality. See the connector pinouts to cross-reference
ADSmartIO signal names.
Electrical specifications for the ADSmartIO are listed in section 6.2.6. The ADSmartIO
Programmer's Reference (ADS document 110110-4004) gives information about how to use the
ADSmartIO features.