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AS8202B

Datasheet - Detailed Descr i p ti on

7.4 TTP Asynchronous Bus Interface

When in asynchronous mode of operation the channel's bus unit uses a self-clocking transmission encoding which can be either MFM or

Manchester at a maximum data rate of 4 Mbit/s on a shared media (physical bus). The pins can either be connected to drivers using recessive/

dominant states on the wire as well as drivers using active push/pull functionality.

The RxD signal uses '1' as the inactivity level. In the so-called RS485 compatible mode longer periods of '0' are treated as inactivity. If the RS485

compatible mode is not used, the application must care to drive RxD to '1' during inactivity on the bus.

7.5 TTP Synchronous Bus Interface

When in synchronous mode of operation, the bus unit uses a synchronous transfer method to transfer data at a rate between 20 and 25 Mbit/s.

The interface is designed to run at 25 Mbit/s and to be fully compatible with the commercial 100 Mbit/s Ethernet MII (Media Independent

Interface) according to IEEE standard 802.3 (Ethernet CSMA/CD).

Connecting the synchronous TTP bus unit to a 100 Mbit/s Ethernet PHY is done by connecting TxD, CTS, TxCLK, RXER, RXCLK, RxDV and

RxD of any channel to TxD0TxD0, TxEN, TxCLK, RXER, RXCLK, RxDV and RxD0 of the PHY's MII. The pins TxD1, TxD2 and TxD3 of the

PHY's MII should be linked to VSS. The signals RxD1, RxD2, RxD3, COL and CRS as well as the MMII (Management Interface) should be left

open or can be used for diagnostic purposes by the application.

Note that the frames sent by the AS8202B are not Ethernet compatible and that an Ethernet Hub (not a Switch) can be used as a 'star coupler'

for proper operation. Also note that the Ethernet PHY must be configured for Full Duplex operation (even though the Hub does not support full

duplex), because TTP has its own collision management that should not interfere with the PHY's Half-Duplex collision management. In general,

the PHY must not be configured for automatic configuration ('Auto negotiation') but be hard-configured for 100 Mbit/s, Full Duplex operation.

Note: To run the interface at a rate other than 25 Mbit/s other transceiver PHY components have to be used.

Table 10. Asynchronous Bus Interface Connections

Pin Name

Mode

Connect to PHY

Note

TxD[0]

out

TxD

Transmit data channel 0

CTS[0]

out

CTS

Transmit enable channel 0

TxCLK[0]

in

No function (do not connect)

RXER[0]

in

No function (do not connect)

RXCLK[0]

in

No function (do not connect)

RxDV[0]

in

No function (do not connect)

RxD[0]

in

RxD

Receive data channel 0

TxD[1]

out

TxD

Transmit data channel 1

CTS[1]

out

CTS

Transmit enable channel 1

TxCLK[1]

in

No function (do not connect)

RXER[1]

in

No function (do not connect)

RXCLK[1]

in

No function (do not connect)

RxDV[1]

in

No function (do not connect)

RxD[1]

in

RxD

Receive data channel 1

Table 11. Synchronous Bus Interface Connections

Pin Name

Mode

Connect to PHY

Note

TxD[0]

out

TxD0TxD0

Transmit data channel 0

CTS[0]

out

TxEN

Transmit enable channel 0

TxCLK[0]

in

TxCLK

Transmit clock channel 0

RXER[0]

in

RXER

Receive error channel 0

RXCLK[0]

in

RXCLK

Receive clock channel 0

RxDV[0]

in

RxDV

Receive data valid channel 0