2

ACS103 Issue 2.03 May 1996.

2

ACS101 Emulation mode using "SEL" input

The "SEL" input pin is normally held Low in order to

configure the device in ACS103 mode. If the "SEL"

input pin is allowed to pull High via an internal

resistor the device will be configured in ACS101

emulation mode.

In ACS101 emulation mode the

device is fully compatible with the ACS101.

The

TxD2, TxD3 and XI3 inputs are internally disabled

with the RxD2, RxD3 and XO3 outputs forced into the

high impedance state. A full-duplex path then exists

between TxD1 and RxD1.

Transmitter and Receiver Functions

The TxD input data of the transmitting modem is

compressed, filtered, and 3B4B encoded.

In the

receiving modem, 3B4B encoding ensures easy

extraction of the bit-clock.

The received data is

filtered, decoded, then stored in an output memory.

The memory provides time expansion, de-jittering

and frequency compensation.

The data is filtered

again to improve BER then directed to the RxD

output pin. Signals TxD and RxD in this specification

refer to the set of signals TxD1/2/3 and RxD1/2/3

respectively.

Transmit Current

The transmit current to the LED can be defined by the

Transmit Current pin (TRC). The current is set to the

maximum

value

(~100 mA)

when

TRC

is

unconnected.

The current is set to the minimum

value (~10 mA) when TRC is connected directly to

ground. To obtain current values between minimum

and maximum, TRC is connected to ground through

a resistor. The resistor value R is given by:

LED current drive (mA) = 100 * (110+R)

(1100 + R)

Data-rate Selection

ACS103 mode SEL = 0

DR4 DR3 DR2 DR1

Data-rate Distance

(kbps)

000

0

n/a

0

0

0

1

9.6

Double

0

0

1

0

19.2

Double

0

0

1

1

38.4

Double

010

0

n/a

010

1

n/a

0

1

1

0

DC - 4.8

Double

011

1

n/a

1

0

0

0

2.4

Standard

1

0

0

1

9.6

Standard

1

0

1

0

19.2

Standard

1

0

1

1

38.4

Standard

1

1

0

0

48.0

Standard

1

1

0

1

56.0

Standard

1

1

1

0

DC - 9.6

Standard

1

1

1

1

64.0

Standard

n/a = not available

The data rates given in the previous table apply to

TxD1, TxD2 and TxD3.

ACS101 mode SEL = 1

DR4 DR3 DR2 DR1

Data-rate Distance

(kbps)

0

0

0

0

256.0

Standard

0

0

0

1

9.6

Double

0

0

1

0

19.2

Double

0

0

1

1

38.4

Double

0

1

0

0

48.0

Double

0

1

0

1

192.0

Standard

0

1

1

0 DC - 19.2

Double

0

1

1

1

64.0

Double

1

0

0

0

2.4

Standard

1

0

0

1

9.6

Standard

1

0

1

0

19.2

Standard

1

0

1

1

38.4

Standard

1

1

0

0

48.0

Standard

1

1

0

1

56.0

Standard

1

1

1

0 DC - 38.4

Standard

1

1

1

1

64.0

Standard

The ACS101 mode is a single channel mode

configuration - the data rates given in the previous

table apply to TxD1 only.

'Standard' mode of operation is up to 2.5 km and

'Double' mode is up to 5 km. The two asynchronous

modes are selected when DR3 = 1, DR2 = 1, DR1= 0.

The above data-rates are obtained when used in

conjunction with a crystal of 9.216 MHz.

Non-

standard data-rates may be generated by using the

appropriate crystal frequency.

For example, to

generate 160 kbps data-rate in ACS101 mode, use a

crystal frequency of: (160/192) * 9.216 MHz, i.e.

7.68 MHz. Other "non-standard" data-rates may be

generated in the same way as long as the 5 - 10 MHz

crystal range is observed.

For the data-rates 9.6, 19.2, and 38.4 kbps in

ACS103 mode (9.6, 19.2, 38.4, 48 and 64 kbps in

ACS101 mode), the data-rate selection pins DR3-

DR1 are common to 'Standard' and 'Double' modes

of operation with DR4 selecting the mode.

Modem Control Signals

RSS.

The RTS/XI1, CTS/XO1, DTR/XI2, DSR/XO2, XI3

and XO3 signals may be used in either of two modes,

depending on the RSS setting:

RSS = Low; data transmission mode

RSS = High; modem handshake mode

RSS Low - Data Transmission Mode.

When configured in data transmission mode the

inputs XI1, XI2 and XI3 are sampled continuously

with the outputs appearing at XO1, XO2 and XO3

(respectively) of the far-end modem.

The sample

frequency for 'Standard' mode is: (crystal freq.)/1536,