topic Re: MC33774 Daisy Chain Dual Loop Connection in Other NXP Products

MC33774 Daisy Chain Dual Loop Connection

Embedded_novice — Mon, 29 Jun 2026 18:26:29 GMT

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.

Re: MC33774 Daisy Chain Dual Loop Connection

ErikaC — Mon, 29 Jun 2026 18:46:45 GMT

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.

Re: MC33774 Daisy Chain Dual Loop Connection

Embedded_novice — Tue, 30 Jun 2026 02:58:29 GMT

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

Re: MC33774 Daisy Chain Dual Loop Connection

ErikaC — Tue, 30 Jun 2026 18:56:39 GMT

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?