78M6612-IMSLASHFSLASHP datasheet(71/111 Pages) TERIDIAN

71 / 111 page

DS_6612_001

78M6612 Data Sheet

Rev. 1.2

3.10 UART1 Interface

The pins TX1 and RX1 can be used for a regular serial interface, e.g. by connecting a RS_232

transceiver, or they can be used to directly operate optical components, e.g. an infrared diode and

phototransistor implementing a FLAG interface. Figure 35 shows the basic connections. The TX1 pin

becomes active when the I/O RAM register TX1DIS is set to 0.

The polarity of the TX1 and RX1 pins can be inverted with configuration bits TX1INV and RX1INV,

respectively.

The TX1 output may be modulated at 38 kHz when system power is present. Modulation is not available

in BROWNOUT mode. The TX1MOD bit enables modulation. The duty cycle is controlled by

OPT_FDC[1:0], which can select 50%, 25%, 12.5%, and 6.25% duty cycle. A 6.25% duty cycle means

TX1 is low for 6.25% of the period.

The receive pin (RX1) may need an analog filter when receiving modulated optical signals.

With modulation, an optical emitter can be operated at higher current than nominal, enabling it to

increase the distance along the optical path.

If operation in BROWNOUT mode is desired, the external components should be connected to

V3P3D.

Figure 35: Connection for Optical Components

3.11 Connecting V1 and Reset Pins

A voltage divider should be used to establish that V1 is in a safe range when the power and

measurement unit is in mission mode (V1 must be lower than 2.9 V in all cases in order to keep the

hardware watchdog timer enabled). For proper debugging or loading code into the 78M6612 mounted

on a PCB, it is necessary to have a provision like the header shown above R1 in Figure 36. A shorting

jumper on this header pulls V1 up to V3P3 disabling the hardware watchdog timer.

The parallel impedance of R1 and R2 should be approximately 8 to 10 k

Ω in order to provide hysteresis

for the power fault monitor.

TX1

78M6612

V3P3SY

Phototransisto

LED

10k

Ω

100pF

V3P3SY

TX1

V3P3SY

Phototransisto

LED

100pF

V3P3SY

78M6612-IM/F/P Datasheet(PDF) 71 Page - Teridian Semiconductor Corporation

78M6612-IM/F/P Datasheet(HTML) 71 Page - Teridian Semiconductor Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL