APPENDIX C

APPLICATION NOTES

RECEIVER CONTROL

Introduction

The FLEXchip IC has 8 programmable receiver control lines (S0–S7). The host has control of the receiver warm up and shut down timing, as well as all of the various settings on the control lines through configuration registers on the FLEXchip IC. The configuration registers for most settings allow the host to configure:

1.what setting is applied to the control lines,

2.how long to apply the setting, and

3.if the LOBAT input pin is polled before changing from the setting.

With this programmability, the FLEXchip IC is able to interface with many off- the-shelf receiver ICs, such as the MC13150 and MC3374. For details on the configuration of the receiver control settings, see Receiver Control Configuration Packets on page B-14.

Receiver Settings at Reset

The receiver control ports are three-state outputs that are set to the highimpedance state when the FLEXchip IC is reset and until the corresponding FRS bit in the Receiver Line Control Packet is set, or until the FLEXchip IC is turned on by setting the ON bit in the Control Packet. This allows the designer to force the receiver control lines to the receiver off setting with external pull-up or pull-down resistors before the host can configure these settings in the FLEXchip IC. When the FLEXchip IC is turned on, the receiver control ports are driven to the settings configured by the Receiver Control Configuration Packets until the FLEXchip IC is reset again.