The 5448 is a layer 2 switch that by default has a native VLAN of 1 with all interfaces in access mode for the native VLAN 1. On the native VLAN all frames are untagged frames. So on your uplink port to the other switch, all info will be sent out untagged, which means the other switch will receive the untagged data and then place it into the VLAN that it is in access mode for. Communication should work fine this way. I would suggest however using a Trunk connection between the switches. The Trunk port is used to connect switches/VLAN aware devices together and allow multiple tagged VLANs across it. It sounds like you may already have multiple VLANs on the network, and having a Trunk connection will allow you to expand on this. At the same time anything that is on the native VLAN will still traverse the Trunk to the other switch and stay on the native VLAN.
Hi,  Just a question.  Will a Dell Powerconnect 5448 switch act like a home switch if its interfaces are set as default with 1 interface connecting to a primary switch who's interface is "interface mode access" with a certain vlan?  Will it work with all its switches on the uplink interface's vlan or would you need to configure the both uplink switch and this switch as trunks to let the access vlan work?
Dell Powerconnect 5448 on Default vlan