SNC558

Two Channel Direct Drive Speech Controller

5 FUNCTION DESCRIPTIONS

5.1. Oscillator

SNC558 accept RC type oscillator for system clock. The typical circuit diagram for

oscillator is listed as follow.

OSC

VCC

RC Oscillator

5.2. ROM

SNC558 contains substantial 64K words (10-bit) internal ROM. Program, voices and

other data are shared with this same 64K words ROM.

5.3. RAM

SNC558 contains 128 nibbles RAM. The 128 nibbles RAM are divided into eight

pages (page 0 to page 7, 16 nibble RAM on each page).

In our programming

structure, users can easily define and locate RAM page in the program. For instance,

users can use the instructions, PAGEn (n=0 to 7) to switch and indicate the RAM page.

Besides, users can use direct mode, M0 ~ M15 in the data transfer type instructions, to

access all 16 nibbles of each page.

5.4. Power Down Mode

“End” instruction will power down SNC558 and enable IC to consume fewer current for

power saving. (<3uA @VDD=3V and <5uA @VDD=5V) Please be aware that when

the power down mode is activated in SNC558, any valid data transition (L H or H L)

occurring on any input port (P1) or IO ports (P2, P3 and P6) will lead SNC558 back to

normal operation mode.

5.5. Sampling Rate Counters

Ver: 1.2

November 26, 2002

3

2 independent sampling rate counters are dedicated to 2 individual voice channels to

be able to play diverse voices at different sample playing rates. The playing rate can

be adaptively set up among from the wide ranges of 2.5KHz to 20KHz. This feature

makes voice close to its original source and yield the better voice quality.