MESSIBLE¶
Messible: An Ansible for Messages
An Ansible is a system for instant communication across vast distances, from a small portable device to a huge terminal far away. A Messible is a message- passing system from embedded devices to a host system. You can use it to get very simple printf()-style support over a debug channel.
The Messible assumes the host has a way to peek into the device’s memory space. This is the case with the Wishbone bridge, which allows both the device and the host to access the same memory.
At its core, a Messible is a FIFO. As long as the STATUS.FULL bit is 0, the
device can write data into the Messible by writing into the IN. However, if this
value is 1, you need to decide if you want to wait for it to empty (if the other
side is just slow), or if you want to drop the message.
From the host side, you need to read STATUS.HAVE to see if there is data
in the FIFO. If there is, read OUT to get the most recent byte, which automatically
advances the READ pointer.
Register Listing for MESSIBLE¶
Register |
Address |
|---|---|
MESSIBLE_IN¶
Address: 0xe0008000 + 0x0 = 0xe0008000
Write half of the FIFO to send data out the Messible. Writing to this register advances the write pointer automatically.
MESSIBLE_OUT¶
Address: 0xe0008000 + 0x4 = 0xe0008004
Read half of the FIFO to receive data on the Messible. Reading from this register advances the read pointer automatically.
MESSIBLE_STATUS¶
Address: 0xe0008000 + 0x8 = 0xe0008008
Field |
Name |
Description |
|---|---|---|
[0] |
FULL |
|
[1] |
HAVE |
|