Specifications

Table Of Contents
ARM Debugger 2 7 A R M S p e c i f i c I m p l e m e n t a t i o n s
©1989-2014 Lauterbach GmbH
Virtual Terminal
The command TERM opens a terminal window which allows to communicate with the ARM core over the
Debug Communications Channel (DCC). All data received from the comms channel are displayed and all
data inputs to this window are sent to the comms channel. Communication occurs byte wide or up to four
bytes per transfer. The four bytes ASCII mode (DCC4A) does not allow to transfer the byte 00. Each non-
zero byte of the 32 bit word is a character in this mode. The four byte binary mode (DCC4B) can be used to
transfer non-ascii 32bit data (e.g. to or from a file). The three bytes mode (DCC3) allows binary transfers of
up to 3 bytes per DCC transfer. The upper byte defines how many bytes are transferred (0 = one byte, 1 =
two bytes, 2 = three bytes). This is the preferred mode of operation, as it combines arbitrary length
messages with high bandwidth. The TERM.METHOD command selects which mode is used (DCC, DCC3,
DCC4A or DCC4B).
The communication mechanism is described e.g. in the ARM7TDMI data sheet in chapter 9.11. Only three
move to/from coprocessor 14 instructions are necessary.
The TRACE32 demo/arm/etc/vitual_terminal directory contains examples for the different ARM families
which demonstrate how the communication works.
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