Pulse Width Modulation Outputs And Tachometer Inputs; External Connections; Pwm Output And Tach Input Code Example - VersaLogic Python EBX-11 Reference Manual

Pulse Width Modulation Outputs and Tachometer Inputs

The EBX-11 incorporates three pulse width modulation (PWM) outputs and three tachometer
(TACH) inputs which can be used, in a limited fashion, as general purpose frequency generators
and counter/timers.
The PWM output frequency options are: 11.0 Hz, 14.6 Hz, 21.9 Hz, 29.3 Hz, 35.2 Hz, 44.0 Hz,
58.6 Hz, 87.7 Hz, 15 kHz, 20 kHz, 25 kHz, and 30 kHz. The PWM duty cycle is user definable
from 0% (1/256) to 100% (255/256) and also invertible.
The SCH3114 Super I/O chip includes a fan speed monitoring feature, which uses TACH inputs.
When the TACHs are set to manual mode, the inputs can be used as counter/timers instead of for
fan speed monitoring. By default, the 16-bit tachometer registers hold the number of 90 kHz
pulses that occur within five tachometer input edge-transitions (e.g., two TACH pulses).
In manual mode, the tachometer circuit begins monitoring the TACH inputs on the 1st edge
detected and continues counting until the last edge is detected. If the counter overflows before
the number of edges is detected, it sets the count to FFFFh. If no edges are detected, a "stalled-
fan event" occurs and the counter is set to FFFFh.
Refer to the SMSC SCH3114 Super I/O datasheet
descriptions.
E C
XTERNAL ONNECTIONS
Table 30: PWM and TACH Connections – Rev. 5.00 and Later Boards*
PWM O
UTPUT AND
The following code provides guidelines for using PWM outputs and tachometer inputs as general
purpose timers. Some steps are designated as required, but all steps are recommended.
;Controlling PWM outputs manually
;Pause the SCH3114 Hardware Monitor (optional)
MOV DX, C70h
MOV AL, 40h
OUT DX, AL
MOV DX, C71h
IN AL, DX
AND AL, FEh
OUT DX, AL
EBX-11 Reference manual
J5
Pin Signal
1 TACH_IN 1
2 TACH_IN 2
3 TACH_IN 3
4 NC
5 GND
6 PWM_OUT 1
7 PWM_OUT 2
8 PWM_OUT 3
9 NC
10 GND
*See Table 6 for the pinout of Rev. 4.xx and earlier boards.
TACH I C E
NPUT ODE XAMPLE
;Hardware Monitor index port
;Ready,Lock,Start Register
;Hardware Monitor data port
;Read Current Value
;Disable Start bit
for more information and detailed register
CBR-4004 CBR-4004
Connector Pin (Signal)
J1 5 (IO1)
TACH 4 (IO2)
3 (IO3)
2 (IO4)
1 (GND1)
J2 5 (IO5)
PWM 4 (IO6)
3 (IO7)
2 (IO8)
1 (GND1)
Interfaces and Connectors
56