Radiometrix Ltd

CTA88

page 3

Decoder Mode

CTA88 can be put into Decoder Mode by connecting TX/RX MODE (pin 4) to ground (0V)

3.58MHz

+5V

supply

470R

470R

470R

100nF

470R

470R

470R

470R

470R

470R

RF

Vcc

GND

RXD

C0

C1

RST

Vss

A0

STB

RXD

OSC1

OSC2

Vdd

A7

A6

A5

A4

Vss

D0

D1

D2

D3

D7

D6

D5

D4

RX MODE

C2

A3

A2

A1

10k array

Figure 3: CTA88 in Decoder Mode

Pin

Name

Input/Output

Description

1

RST

Input

Active Low Reset (Connect to user system reset or tie to Vdd)

2

RXD

Output

baseband DATA from receiver module’s RXD output

3

STB

Output

Valid data burst detect pulse (36mS long).

4

TX/RX MODE

Input

tie to Vss = RX mode

5

C0

Input

6

C1

Input

7

C2

Input

8

Vss

Supply

Supply Ground

9

OSC1

Output

10

OSC2

Input

11 - 18

D0 - D7

Output

8 bits of Data Outputs

19

Vss

Supply

Supply Ground

20

Vdd

Supply

4.0V-5.5V supply (decouple with 100nF close to IC).

2.0V-5.5V (low voltage version)

21 - 28

A0 – A7

Input

Notes:

1. OSC1, 2 require a 3.58MHz ceramic resonator like KBR-3.58MKS (internal caps, ground middle

pin).

If a 2 pin resonator or crystal is used, then two 15pF caps are needed : one from OSC1 to 0V ;

one from OSC2 to 0V

2. Data and Address pins are logic true (1=VCC, 0=0V) inputs and outputs

3. Address inputs have weak pullups to Vcc and are schmitt trigger inputs

4. C0-C2 (pins 5-7) are active high and have no pullups.

5. A 1kbps bi-phase communications protocol is used, compatible with all Radiometrix Wireless

modules

6. A databurst is approximately 110mS long

7. After asserting TX on high (active), the coder allows 50mS for TX to power up and settle

8. Pin 4 (TX/RX MODE) has no pullup.

9.

Without external loads the chip draws less than 2mA from 5v