ST7MC1 datasheet(164/308 Pages) STMICROELECTRONICS

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ST7MC1/ST7MC2

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MOTOR CONTROLLER (Cont’d)

10.6.6.13 Encoder Mode (IS[1:0] = 11)

Figure 90 shows the signals delivered by a stand-

ard digital incremental encoder and associated in-

formation:

– Two 90° phased square signals with variable

frequency proportional to the speed; they

must be connected to MCIA and MCIB input

pins,

– Clock derived from incoming signal edges,

– Direction information determined by the rela-

tive phase shift of input signals ( + or -90°).

The Incremental Encoder Interface block aims at

extracting these signals. As input logic is both ris-

ing and falling edge sensitive (independently from

TES[1:0] bits setting), resulting clock frequency is

four times the one of the input signals, thus in-

creasing resolution for measurements.

It may be noticed that Direction bit (EDIR bit in

MCRC register) is read only and that it does’nt af-

fect counting direction of clocked timer (cf Section

). As a result, one cannot extract position informa-

tion from encoder inputs during speed reversal.

Figure 89. Tacho Capture events configured by the TES[1:0] bits

Figure 90. Incremental Encoder output signals and derived information

Tacho

input

Tacho

Capture

TES[1:0]=11

TES[1:0]=01

TES[1:0]=10

MCIA

MCIB

Encoder

inputs

Encoder

Direction

Clock

Sampling of MCIA to determine direction

(EDIR bit)

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