Zilog Z80230 User Manual

Page 178

SCC/ESCC

User Manual

UM010903-0515

171

Set FM Mode Command (110).

This command forces the DPLL to operate in the FM mode and

is used to recover the clock from FM or Manchester-Encoded data. (Manchester is decoded by

placing the receiver in NRZ mode while the DPLL is in FM mode.)

Set NRZI Mode Command (111).

Issuing this command forces the DPLL to operate in the NRZI

mode. This mode is also selected by a hardware or channel reset.

Bit 4: Local Loopback select bit

Setting this bit to 1 selects the Local Loopback mode of operation. In this mode, the internal trans-

mitted data is routed back to the receiver, and to the TxD pin. The /CTS and /DCD inputs are

ignored as enables in Local Loopback mode, even if auto enable is selected. (If so programmed,

transitions on these inputs still cause interrupts.) This mode works with any Transmit/Receive

mode except Loop mode. For meaningful results, the frequency of the transmit and receive clocks

must be the same. This bit is reset by a channel or hardware reset.

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