First Commit

externals/teakra/src/ahbm.md

@@ -0,0 +1,37 @@
+# AHBM
+
+## MMIO Layout
+
+```
+Status register
++-----------#---+---+---+---#---+---+---+---#---+---+---+---#---+---+---+---#
+|+0x00E0    |   |   |   |   |   |   |   |   |   |   |   |   |   |RNE|   |   |
++-----------#---+---+---+---#---+---+---+---#---+---+---+---#---+---+---+---#
+Applications wait for all bits to be 0 before connecting AHBM to DMA
+RNE: 1 when the burst queue is not empty
+
+Channel config (N = 0, 1, 2)
++-----------#---+---+---+---#---+---+---+---#---+---+---+---#---+---+---+---#
+|+0x00E2+N*6|       -       |   |   |   |   |   | - | TYPE  |   | BURST | R |
++-----------#---+---+---+---#---+---+---+---#---+---+---+---#---+---+---+---#
+|+0x00E4+N*6|           -           | E | W |   |   |   |   |   |   |   |   |
++-----------#---+---+---+---#---+---+---+---#---+---+---+---#---+---+---+---#
+|+0x00E6+N*6|               -               | D7| D6| D5| D4| D3| D2| D1| D0|
++-----------#---+---+---+---#---+---+---+---#---+---+---+---#---+---+---+---#
+R: Applications set this to 1 if BURST is non-zero
+BURST: burst type
+ - 0: x1
+ - 1: x4
+ - 2: x8
+ - 3: ?
+TYPE: data type
+ - 0: 8 bit
+ - 1: 16 bit
+ - 2: 32 bit
+ - 3: ?
+W: Transfer direction
+ - 0: read from external memory
+ - 1: write to external memory
+E: Applications always set this.
+D0..D7: Connects to DMA channel 0..7 if set to one
+```