SM1126 Series

NIPPON PRECISION CIRCUITS—13

Parity check command

Data words (tempo word, melody words, end word) can have an optional parity bit added, forming 9-bit data

words, for a parity check function. The parity check command is executed in play mode, immediately after the

end-of-write command is executed.

The parity bit is added at the beginning of the data word. Note that the last 8 bits are always the valid data

bits. The parity check function performs an odd parity check (an odd number of 1s within the 9-bit data). If the

parity check command is not executed, play mode operation continues using the valid 8 bits of data in each

data word.

The parity check sequence is described below.

1. The internal G flag (Good flag) is set to 1 when the write command is executed.

2. When writing data words, the G flag remains set to 1 for odd parity, but is set to 0 if even parity is detected.

3. The G flag remains set to 1 only if all data words have odd parity.

4. Write the end-of-write command to return to play mode.

5. Write the parity check command.

6. When ST is HIGH, the SIO pin functions as the G flag output.

7. When ST goes LOW, the G flag output is released.

Figure 15. Parity check timing

SIO

SC

ST

MODE

SIO Condition

G Flag

WRITE mode

Input

PLAY mode

01

11

1

1

1

1

11

01

1

1

1

1

END-WRITE mode command

Parity Check Command

Input

Output

When G Flag = 1

When G Flag = 0