IC-PI datasheet(39/49 Pages) ICHAUS

39 / 49 page

preliminary

iC-PI PROGRAMMABLE 12-BIT

Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

Rev B1, Page 39/48

ERROR MONITORING AND ALARM OUTPUT

iC-PI monitors the input signals, the internal interpolator

and the sensor supply controller through which the input

signal levels are stabilized. If the sensor supply tracking

unit reaches its control limits this can be interpreted as

an end-of-life message, for example.

Three separate error masks stipulate whether error

events are signaled as an alarm via I/O pin ERR (mask

EMASKA), whether they cause the (RS422) output

drivers to shutdown or not (mask EMASKO) or whether

they are stored in the EEPROM (mask EMASKE).

Alarm Output: I/O-pin ERR

Pin ERR is operated by a current-limited open-drain

output driver and has an internal pull-up which can be

disabled. The ERR pin also acts as an input for ex-

ternal system error messaging. Interpretation of an

external system error message and the phase of the

message output is configured by EPH and the minimum

indication time by EMTD.

EPH

Addr. 0x1A, bit 4

Code

State on error

State w/o error

active low

high impedance,

with input function for a

low-active system error;

high impedance

active low

Notes

*) Pin ERR is disabled during driver shutdown and

cannot indicate errors in this case.

Table 61: I/O Logic, Alarm Output ERR

EMTD

Addr. 0x18, bit 6:4

Code

Indication Time

Code

Indication Time

0x0

0 ms

0x4

50 ms

0x1

12.5 ms

0x5

62.5 ms

0x2

25 ms

0x6

75 ms

0x3

37.5 ms

0x7

87.5 ms

Table 62: Min. Indication Time, Alarm Output ERR

EPU

Addr. 0x1A, bit 5

Code

Function

No internal pull-up

Internal 300 µA pull-up current source active

Table 63: Pull-Up Enable, Alarm Output ERR

EMASKA

Addr. 0x18, bit 1:0; Addr. 0x17, bit 7:0

Bit

Error event

Line count error:

wrong count of sine periods between two zero pulses

Excessive output lag:

output angle differs from actual input angle, e.g.

after cycling power, when exceeding the maximum

input frequency, when the output frequency is limited

due to the minimum edge distance (MTD)

Excessive input frequency:

angle lost by interpolation engine (at ≈ 600 kHz***)

6 *

Configuration error:

checksum error, no acknowledge signal from

EEPROM, or SDA or SCL pin error.

Excessive temperature warning

Ungated index enable signal ZIn

(comparated X1/X2 inputs for CFGABZ and

CFGZPOS adjustment, at EMTD = 0x0)

Control range at max. limit (control error 2)

Control range at min. limit (control error 1)

Signal clipping (signal error 2)

Loss of signal (signal error 1):

poor differential amplitude**, wrong s/c phase.

Code

Function

Enable: event changes state of pin ERR

(if EMASKO does not disable the output function).

Disable: event does not affect pin ERR.

Notes

*) Pin ERR can not pull low on configuration error,

use high-active error logic instead (EPH = 1);

**) Also due to excessive input signals or internal

signal clipping.

***) Limit does not depend on IPF or MTD, just on

the chip’s system clock. This error indicates that the

digital engine is not able to capture the input signals

anymore.

Table 64: Error Mask Alarm Output ERR

Line Count Error

Line count monitoring is of particular importance for en-

coder systems. iC-PI counts the number of sine cycles

between two adjacent zero pulses and compares it to

the reference value LINECNT. In case of a deviation,

the line count error is set. The check is paused if the

direction of rotation changes, and is restarted on the

next zero pulse.

LINECNT

Addr. 0x24, bit 5:0; Addr. 0x23, bit 7:0

Code

Function Value

Line Count (CPR)

0x0000

...

Code + 1

0x3FFF

16383

16384

Example

Code disc of 256 CPR → LINECNT = 255

Table 65: Line Count Reference

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