+# Adding a "Slow" Peripheral
+
+This example will be cheating by cut/paste copying an existing very
+similar interface, SD/MMC. The SD/MMC interface is presently a "dummy"
+that will be extended later. However given that the peripherals are
+so very very similar, common base classes will be used, in a style that
+has also been used in SPI/QSPI and also UART.
+
+## Adding the pin specifications
+
+Looking at src/spec/pinfunctions.py we find that an emmc function actually
+already exists. So unlike sdram, there are no modifications to be made.
+We can check that it works by creating an example, say in src/spec/i\_class.py
+by adding an emmc interface to Bank B:
+
+ ps.gpio("", ('B', 0), 0, 0, 18)
+ ps.flexbus1("", ('B', 0), 1, spec=flexspec)
+ ps.emmc("", ('B', 0), 3) <---
+
+ ps.flexbus2("", ('C', 0), 0)
+
+