VersaLogic EBX-22 Reference Manual page 74

OUT DX, AL
MOV DX, C71h
IN AL, DX
AND AL, F1h
OUT DX, AL
;Re-start the SCH3114 Hardware Monitor (required)
MOV DX, C70h
MOV AL, 40h
OUT DX, AL
MOV DX, C71h
IN AL, DX
OR AL, 1h
OUT DX, AL
;Reading FanTachs
;Read FanTach LSB first then read the latched MSB
; fantach 1 LSB = 28h
; fantach 1 MSB = 29h
; fantach 2 LSB = 2Ah
; fantach 2 MSB = 2Bh
; fantach 3 LSB = 2Ch
; fantach 3 MSB = 2Dh
;
MOV DX, C70h
MOV AL, 28h
OUT DX, AL
MOV DX, C71h
IN BL, DX
MOV DX, C70h
MOV AL, 29h
IN BH, DX
;BX now contains 16-bit number of 90KHz pulses that
;were counted within 5 edges (2 pulses) of the tach input.
;Input Frequency f = 1 / (BX * 11.11uS / 2), RPMs = f * 60
EBX-22 Reference Manual
;Read Current Value
;Set to 14.6 Hz
;Hardware Monitor index port
;Ready,Lock,Start Register
;Hardware Monitor data port
;Read Current Value
;Enable Start bit
;FanTach 1 LSB
;FanTach 1 MSB
Interfaces and Connectors
68