SNC688

4-Channel Speech Controller

5. FUNCTION DESCRIPTIONS

5.1 Oscillator

SNC688 accepts crystal oscillator / ceramic resonator or RC type oscillator (selected

by pin CKSEL) for system clock. The typical circuit diagrams for oscillator are listed as

follows.

CKS EL

VDD

XOUT/ROS C

XIN

CKS EL

XOUT/ROS C

XIN

100K

SNC 688

SNC 688

8MHZ Crystal

8M Rosc

5.2 ROM

SNC688 contains 184K words (12-bit) internal ROM. Program, voices, melodies, data,

and instrument waveforms share the same ROM with the others.

5.3 RAM

SNC688 contains 256 nibble RAM. The 256 nibble RAM is separated into four pages

(page 0, page1, page2 and page 3). An implicit page indicator is utilized to specify

page address. Four instructions, PAGE0, PAGE1, PAGE2 and PAGE3, can switch

the page indicator. All 64 nibbles of each page can be accessed by direct mode (to

specify M0 ~ M63 in the data transfer type instructions.)

5.4 Power Down Mode

“End” instruction will let SNC688 enter power down mode and consumer very little

amount of current. (<3uA @VDD=3V and <5uA @VDD=5V) After SNC688 enters

power down mode, any valid data transition (L H or H L) occurring on any IO ports

(P1 to P6) lead SNC688 back to normal operation mode.

5.5 Sampling Rate Counters

4 independent sampling rate counters are dedicated to 4 individual voice channels to

play voices with different playing rates. The playing rate is programmable from 4KHz

to 40KHz. The resolution of sampling period of each sampling rate counter is 0.25 uS.

This feature helps SNC688 play sounds with accurate pitches in the case of music

instrument synthesis.

Ver: 1.2

August 26, 2003

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