SuperH (SH) 64-bit RISC Series SH-5 System Architecture, Volume ...

PRELIMINARY DATA
SHdebug link 207
DBUS messages
A DBUS message is sent from SH-5 whenever the CPU or another bus master issues
requests to the debug module’s SuperHyway target address space. For each request
message sent from SH-5 there is a corresponding response message sent back from
the external debug adapter or development host. The DBUS request message has
the same format as the originating SuperHyway message but with the addition of a
header to identify it as a DBUS message.
The message type field occupies the least-significant 3-bits of the first byte of the
message. The remaining 5-bits of this first byte are unused.
DTRC messages
There are two types of DTRC messages:
• trigger trace messages (message type MHDR_DTRC_TRIG == 0b011)
• background trace messages (message type MHDR_DTRC_BACK == 0b010).
They are distinguished by the message type field, but contain exactly the same data.
The debug adapter can perform different functions with these two types of trace
message (using a different message type field simplifies the design of the debug
adapter as the message header allows a simple comparison to be made).
Typically, the debug adapter will store background trace messages in a trace buffer
memory area for later analysis but will forward trigger trace messages to debug
software running on the development host for immediate processing.
DTRC transactions are output-only and require no response.
DTRC message from SH-5
Bit 0
Message
Type field
D R A FT
Trace Information
BitN
Figure 9: DTRC protocol
No Response
05-SA-10003 v1.0
SuperH, Inc.
SH-5 System Architecture, Volume 3: Debug