6

Functional description

6.1

Parallel interface

The integrated smart parallel interface offers three interfacing signals easily managed by a micro-controller. The

LOAD signal enables the input buffer storing the value of the channel inputs. The SYNC signal copies the input

buffer value into the transmission buffer and manages the synchronization between low voltage side and the

channel outputs on the isolated side.

The OUT_EN signal enables the channel outputs. An internal refresh signal updates the configuration of the

channel outputs with a frefresh frequency. This signal can be disabled forcing low the SYNC input when LOAD is

high. SYNC and LOAD pins can be in direct control mode (DCM) or synchronous mode (SCM). The operation of

these two signals is described as follows:

Table 14. Interface signal operation (general)

LOAD

SYNC

OUT_EN

Device behavior

Don't care Don't care

Low(1)

The outputs are disabled (turned off)

High

High

High

The outputs are left unchanged

Low

High

High

The input buffer is enabled, the outputs are left unchanged

High

Low

High

The internal refresh signal is disabled, the transmission buffer is updated and the outputs

are left unchanged

Low

Low

High

The device operates in direct control mode as described in section 7.2 Direct Control Mode

(DCM)

1. The outputs are turned off on OUT_EN falling edge and they are kept disabled as long as it is low

6.1.1

Input signals (IN1 to IN8)

Inputs from IN1 to IN8 are the driving signals of the corresponding OUT1 to OUT8 outputs. Data are directly

loaded on related outputs if SYNC and LOAD inputs are low (DCM operation) or stored into input buffer when

LOAD is low, and SYNC is high.

6.1.2

Load input data (LOAD)

The input is active low; it stores the data from IN1 to IN8 into the input buffer

6.1.3

Output synchronization (SYNC)

The input is active low; it enables the integrated transmission buffer loading input buffer data and manages the

transmission between the two isolated sides of the device.

ISO808, ISO808-1

Functional description

DS14169 - Rev 1

page 15/38