NEC mPD780973 Series Preliminary User's Manual page 208

Figure 17-3. Sound Generator Control Register (SGCR) Format
Address: FF94H After Reset: 00H
Symbol 7
SGCR TCE
TCE
0 Timer operation stopped
SGOF/SGO and SGOA for low-level output
1 Sound generator operation
SGOF/SGO and SGOA for output
Caution Before setting the TCE bit, set all the other bits.
Remark SGOF: Basic cycle signal (without amplitude)
SGO: Basic cycle signal (with amplitude)
SGOA: Amplitude signal
SGOB
0 Selects SGOF and SGOA outputs
1 Selects SGO and PCL outputs
SGCL2
0
0
1
1
SGCL0
0 f
1 f
Cautions 1. When rewriting SGCR to other data, stop the timer operation (TCE = 0) beforehand.
2. Bits 4 to 6 must be set to 0.
208
CHAPTER 17 SOUND GENERATOR
R/W
6 5 4
0 0 0
Sound Generator Operation Selection
Sound Generator Output Selection
SGCL1 5-Bit Counter Input Frequency f
0
5
f = f /2
SG2 SG1
6
1 f = f /2
SG2 SG1
7
0 f = f /2
SG2 SG1
8
1 f = f /2
SG2 SG1
Sound Generator Input Frequency Selection
= f /2
SG1 X
= f
SG1 X
3 2 1
SGOB SGCL2 SGCL1
Selection
SG2
0
SGCL0