CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Telephone Function)

CHFO: R13 output selection register (FF13H•D3)

Selects the R13 terminal function.

When "1" is written: HFO output

When "0" is written: General-purpose DC output

Reading: Valid

When using the R13 terminal for the HFO output, write "1" to this register. Furthermore, fix the R13 register at "1" and the R13HIZ register at "0".

The HFO output is controlled by the HF register (FF14H•D3). At initial reset, this register is set to "0".

OSCC: OSC3 oscillation control (FF00H•D2)

Controls the OSC3 oscillation.

When "1" is written: OSC3 oscillation ON

When "0" is written: OSC3 oscillation OFF

Reading: Valid

When it is necessary to activate the DTMF generator or to operate the CPU at high speed, set OSCC to "1". At other times, set it to "0" to reduce current consumption. At initial reset, this register is set to "0".

TPS: Tone/Pulse mode selection (FF10H•D3)

Selects a dialing mode.

When "1" is written: Pulse mode

When "0" is written: Tone mode

Reading: Valid

When "1" is witten to the TPS register, pulse mode (outputs dial pulses) is selected. When "0" is written, tone mode (outputs tone signals) is selected.

At initial reset, this register is set to "0".

MB: Make/Break ratio selection (FF10H•D1)

Selects a make ratio for pulse mode.

When "1" is written: 33.3 : 66.6

When "0" is written: 40.0 : 60.0

Reading: Valid

The make ratio (make : break) of the dialing pulses that are generated from the DP generator is set. When

"1" is written to the MB register, 33.3 : 66.6 is set. When "0" is written, 40.0 : 60.0 is set. The DP generator produces the dialing pulses as "Make" (High) period is before "Break" (Low) period.

This selection is valid only for pulse mode. At initial reset, this register is set to "0".

DRS: Dialing pulse rate selection (FF10H•D0)

Selects a dialing pulse rate for pulse mode.

When "1" is written: 20 pps (pulses per second)

When "0" is written: 10 pps (pulses per second)

Reading: Valid

The pulse rate (number of pulses per second) for the dialing pulses that are generated from the DP generator is set. When "1" is written to the DRS register, 20 pps is set. When "0" is written, 10 pps is set. This selection is valid only for pulse mode.

At initial reset, this register is set to "0".

S1C63558 TECHNICAL MANUAL

EPSON

129