W83194R-37 Datasheet, PDF (7/19 Pages) Winbond – 100 MHZ AGP CLOCK FOR VIA CHIPSET

Preliminary W83194R-37/-58
8.3 Serial Control Registers
The Pin column lists the affected pin number and the @PowerUp column gives the state at true
power up. Registers are set to the values shown only on true power up. "Command Code" byte and
"Byte Count" byte must be sent following the acknowledge of the Address Byte. Although the data
(bits) in these two bytes are considered "don't care", they must be sent and will be acknowledge. After
that, the below described sequence (Register 0, Register 1, Register 2, ....) will be valid and
acknowledged.
8.3.1 Register 0: CPU Frequency Select Register
BIT @POWERUP PIN
DESCRIPTION
7
0
- 0 = ±1.5% Spread Spectrum Modulation (W83194R-37)
1 = ±0.5% Spread Spectrum Modulation
0 = ±0.25% Center Type Spread Spectrum Modulation (W83194R-58)
1 = ±0.5% Center Type Spread Spectrum Modulation
6
0
- SSEL2 (Frequency table selection by software via I²C)
5
0
- SSEL1 (Frequency table selection by software via I²C)
4
0
- SSEL0 (Frequency table selection by software via I²C)
3
0
- 0 = Selection by hardware
1 = Selection by software I²C - Bit 6:4
2
0
- SSEL3 (Frequency table selection by software via I²C for
W83194R-58)
2
0
- 0 = Spread spectrum center type (W83194R-37)
1 = Spread spectrum down type (W83194R-37)
1
0
- 0 = Normal
1 = Spread Spectrum enabled
0
0
- 0 = Running
1 = Tristate all outputs
W83194R-37 Frequency table selection by software via I²C
SSEL2 SSEL1 SSEL0
CPU(MHz)
SDRAM
SD_SEL=1
(MHz)
SD_SEL=0
0
0
0
60
60
60
0
0
1
66.8
66.8
66.8
0
1
0
68.5
68.5
68.5
0
1
1
75
75
75
1
0
0
75
75
60
1
0
1
83.3
83.3
66.6
1
1
0
95
95
63.4
1
1
1
100
100
66.6
PCI
(MHz)
30
33.4
34.25
37.5
30
33.3
31.7
33.3
AGP
(MHz)
60
66.8
68.5
75
60
66.6
63.4
66.6
REF (MHz)
14.318
14.318
14.318
14.318
14.318
14.318
14.318
14.318
Publication Release Date: April 1999
-7-
Revision A1