1. An apparatus to control an external interface in an integrated circuit, the apparatus comprising: a controller configured to communicate on the external interface; a command queue configured to store a plurality of commands that cause a transfer on the external interface; a macro memory configured to store a second plurality of commands forming a macro; and a control circuit coupled to the command queue, the macro memory, and the controller, wherein the control circuit is configured to read the plurality of commands from the command queue and is configured to initiate corresponding operations in the controller to perform the transfer, and wherein the control circuit is configured to invoke the macro responsive to detecting a macro command within the plurality of commands from the command queue, wherein the macro command includes a length operand specifying a length of the macro, and wherein the control circuit is configured to return to the plurality of commands in the command queue responsive to completing the macro as specified by the length operand, and wherein the macro excludes an explicit return command.