SCH3112 Datasheet, PDF (275/396 Pages) SMSC Corporation – LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports

LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports
Datasheet
Bit[7:5] Reserved
24.2.41 Registers 94h-96h: PWMx Option Registers
Register
Address
94h
95h
96h
Read
/Write
R/W
R/W
R/W
Register
Name
PWM1 Option
PWM2 Option
PWM3 Option
Bit 7 Bit 6 Bit 5
(MSb)
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
(LSb)
Default
Value
RES RES OPP GRD1 GRD0 SZEN UPDT1 UPDT0 0Ch
RES RES OPP GRD1 GRD0 SZEN UPDT1 UPDT0 0Ch
RES RES OPP GRD1 GRD0 SZEN UPDT1 UPDT0 0Ch
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
Bits[1:0] Tachs reading registers associated with PWMx are updated: (Mode 2 only)
00=once a second (default)
01=twice a second
1x=every 300msec
Bit[2] Snap to Zero (SZEN)
This bit determines if the PWM output ramps down to OFF or if it is immediately set to zero.
0=Step Down the PWMx output to Off at the programmed Ramp Rate
1=Transition PWMx to Off immediately when the calculated duty cycle is 00h (default)
Bit[4:3] Guard time (Mode 2 only)
00=63 clocks (90kHz clocks ~ 700usec)
01=32 clocks (90kHz clocks ~ 356usec) (default)
10=16 clocks (90kHz clocks ~ 178usec)
11=8 clocks (90kHz clocks ~ 89usec)
Bit[5] Opportunistic Mode Enable
0= Opportunistic Mode Disabled. Update Tach Reading once per PWMx Update Period (see Bits[1:0]
in this register)
1=Opportunistic Mode is Enabled. The tachometer reading register is updated any time a valid
tachometer reading can be made during the ‘on’ time of the PWM output signal. If a valid reading is
detected prior to the Update cycle, then the Update counter is reset.
Bit[7:6] Reserved
24.2.42 Register 97h: SMSC Test Register
Register Read
Address /Write
97h
R/W
Register Name
SMSC Test Register
Bit 7 Bit 6
(MSb)
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1 Bit 0 Default
(LSb) Value
TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0
5Ah
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
This is an SMSC Test Register. Writing to this register may cause unwanted results.
SMSC SCH311X
259
DATASHEET
Rev 0.2 (09-28-04)