CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Telephone Function)

4.14.7 Flash

The flash function pulls down the DP terminal to Low level for a predetermined period of time to temporarily restore the telephone to on-hook status. The flash time should be set to the FTS3–FTS0 register (FF12H). Table 4.14.7.1 lists the available flash time.

Table 4.14.7.1 Flash time selection

 

FTS

 

Flash time

D3

D2

D1

D0

(msec)

0

0

0

0

Unavailable *

0

0

0

1

94

0

0

1

0

188

0

0

1

1

281

0

1

0

0

375

0

1

0

1

469

0

1

1

0

563

0

1

1

1

656

 

FTS

 

Flash time

D3

D2

D1

D0

(msec)

1

0

0

0

750

1

0

0

1

844

1

0

1

0

938

1

0

1

1

1031

1

1

0

0

1125

1

1

0

1

1219

1

1

1

0

1313

1

1

1

1

1406

Do not write "0" (0000B) to the FTS register because it may cause a malfunction. At initial reset, the flash time is set to 563 msec.

Writing data to the FTS register just defines the flash time. The actual flash operation will be activated when the FLASH bit (FF14H•D0) is set to "1".

Figure 4.14.7.1 shows a timing chart of the flash function.

HSON (FF18H•D3)

Data bus

Write to TPS (FF10H•D3)

Write to TCD (FF17H)

Write to FLASH (FF14H•D0)

DP

TONE

XRMUTE(R11)

XTMUTE(R10)

Interrupt request

"0"

Flash

1

Flash

2

Pulse mode Tone mode

"1"

"0'

"0"

"0"

tFL

 

tFLP

 

tIDP

 

tFL

 

tFLP

"0"

"1"

tMH

"1"

tFL: Flash time

tFLP: Flash pause time

tIDP: Inter-digit pause time

tMH: Mute hold time

Fig. 4.14.7.1 Flash execution timing chart

124

EPSON

S1C63558 TECHNICAL MANUAL