Datasheet

DS_INLC10AQ Revision 1.0_B

Inova Semiconductors Confidential

Page 20 of 35

4.1.7 Read Access

A read access consists of two phases, the command and the response phase. The command phase uses

downstream communication and the response phase uses upstream communication. Commands for read

access do not use the command address, i.e. these commands may not be directed to a device based on

the device address.

There are two commands for read access, digLED_Read and digLED_Ping. The digLED_Read commands

retrieve a status information from all devices and the digLED_Ping command is used to check the device

chain’s integrity. Only the final node in the chain responds to a PING command.

A digLED_Read command is first received by all devices via the frame in downstream direction. The last

node in the chain then immediately transmits its response frame upstream. The response frame’s data field

depends on the actual digLED_Read command. The response frame’s address field is set according to the

own device’s address. All the nodes upstream forward all received response frames until a frame with the

address of their adjacent node is received. Then the respective node transmits its own response frame. This

procedure lasts until the chain’s first node has transmitted its response frame.

A digLED_Ping command is similar to a digLED_Read command, but only the last device in the chain

responds to a digLED_Ping. Thus, the digLED_Ping command is executed much faster than a regular

digLED_Read command.

Figure 15 - Single ended read command and responses

Name

Description

Equation

tDS_US

Delay between down- and upstream

tDS_CL + tUS_CL + 2 x n x tPD

tRESP

Delay between responses

Oscillator variation of adjacent devices < ±30%

Oscillator variation of adjacent devices > ±30%

0.43 x tUS_CL

0.7 x tUS_CL

Table 18 - Down- and upstream delay, delay between responses