Figure 1. TOIM3000 – UART interface
(built-in infrared port)
pin 4, DTR
pin 7, RTS
pin 3, TXD
pin 2, RXD
Figure 2. TOIM3232 – RS232 port interface
(external infrared adapter)
Figure 1 shows a typical example of a UART interface.
As shown, XIN accepts the 1.8432 MHz input clock, and
B_CLK accepts the 16 times baud rate clock.
Set S1 = S0 = LOW (“0”). When RESET = 0, the
TOIM3000 sends the data to, or receives the data from the
infrared transceiver TFDS3000. If Reset is active,
RESET = 1, the TOIM3000 handles the normal electrical
data exchange with the RS232 port.
W R1 = 2.2 k optional (only necessary when RxD–RD IR
line is capacitive loaded).
R2 = 100 W, R3 = 10 W, C1 = 6.8 mF and C2 = 0.1 mF. C1
and C2 are in parallel (VCC = 5 V, in case of 3 V supply,
value of R3 should be reduced, see introductory text).
Single clock operation
TOIM3000 can be operated with only a single clock. In
this case, B_CLK and XIN are tight together and con-
nected to the Baudout pin of the UART. The pulse width
is then shortened to 3/16 of the bit length and noise filter-
ing is deactivated. S1 should be connected to VCC and SO
Figure 2 shows a typical example of an RS232 port inter-
face. The TOIM3232 interfaces the RS232 port to an
infrared transceiver. Due to the various voltage levels, an
additional level converter (discrete or integrated) is nec-
sessary. The baud rate generator is programmable. A
description of programming is given in the Chapter “Soft-
ware for the TOIM3232” page 7 (IrDA Design Guide).
When BR/D = 0, the TOIM3232 interprets RD_232 data
as data transmitted to the TFDS3000. On the other hand,
whenever BR/D = 1, the TOIM3232 interprets RD_232
as the control word. The baud rate can be programmed to
operate from 1200 bit/s to 115 kbit/s. As RS232 level
converter, EIA232 or MAX232 or equivalent should be
The external resistors and capacitors needed are shown in
figure 1. Please also refer to figure 1 for the recom-
mended power supply filter and pull-up resistors.
The output pulse length can be programmed, see chapter
“Operation Description”. It is strongly recommended to
m use 1.627 s output pulses to save battery power.
Rev. A4, 26-Mar-96