MC33774 Daisy Chain Dual Loop Connection

[Embedded_novice]

HI.

我当前使用MC33665A+MC33774的AFE采样系统组成双链回环的结构，配置MC33665A的PORT0和PORT1分别为MADD0和MADD1，当前发送所有指令均由MADD0发送。当我只连接PORT0到DC1之间的菊花链时，我的通讯都是正常的，但是当我把PORT1和DC2之间的菊花链也连接后，我再去请求33774发现33774无法回复响应帧，这是为什么？我回读确认过33665的PORT端口配置没有错误，并且将33774中的SYS_TPL_CFG.RESPCFG设置为00 SAME模式。

I am currently using an AFE sampling system consisting of the MC33665A + MC33774 in a dual-ring loop configuration. I have configured PORT0 and PORT1 of the MC33665A as MADD0 and MADD1, respectively, and all commands are currently sent through MADD0.

When I connect only the daisy chain between PORT0 and DC1, communication works correctly. However, after I also connect the daisy chain between PORT1 and DC2, the MC33774 no longer responds when I send requests to it.

Why does this happen?

I have read back and verified that the MC33665 PORT configuration is correct, and I have configured SYS_TPL_CFG.RESPCFG = 00 (SAME mode) in the MC33774.

[ErikaC]

Hello,

According to the AN13910 TPL Loopback Recommendation, when two MC33665A TPL ports are connected as a loopback ring, there are several configuration requirements that may cause the behavior you are seeing.
For a loopback configuration:

• We recommend assigning device addresses (DADD) in ascending order from one side of the ring and in reverse order from the loopback side (I do not see this in your image).
• If two ports are connected as loopback, one of the ports should have SYS_PORTx_CFG[RX] = 0 to avoid duplicate data entering the MC33665 buffer.
• In addition, one of the ports should have SYS_PORTx_CFG[ALLCHAINS] = 0. If both loopback ports accept ALLCHAINS commands, document states that this can cause signal conflicts and communication errors.

Could you please share the values of SYS_PORT0_CFG and SYS_PORT1_CFG (especially EN, RX, ALLCHAINS, MADD, and CADD)? That would help determine whether the loopback ports are configured according to the AN13910 recommendations.

[Embedded_novice]

HI.

1.我想知道从MADD=1的位置反向分配DADD是必须的吗？

2.我当前的SYS_PORT0_CFG配置为TIMEOUT=0,CADD=1,MADD=0,PROTOCOL=1,ALLCHAINS=1,TERM=1,RX=1,EN=1

SYS_PORT1_CFG配置为TIMEOUT=0,CADD=1,MADD=1,PROTOCOL=1,ALLCHAINS=1,TERM=1,RX=1,EN=1

[ErikaC · Accepted solution]

Hello,

According to AN13910 TPL Loopback Recommendation, the DADD assignment should be reversed from the MADD=1 side in a loopback topology.

In addition, your current configuration has RX=1 and ALLCHAINS=1 on both ports. For a loopback connection, we recommend disabling RX and ALLCHAINS on one of the ports to avoid duplicate routing and communication conflicts. 

Could you please try configuring one port with RX=0 and ALLCHAINS=0 (for example, PORT1) and verify whether the MC33774 starts returning response frames?