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October 13 1995, Draft 1
398
Addendum to –– Evaluating and Programming the 29K RISC Family
ROM emulators always provide a second access port to the emulated memory.
Via this second port, the contents of the memory can be read or written. This is
generally accomplished by a host computer to which the ROM emulator is attached.
The technique enables programs to be installed in system memory without the need
to prepare (often termed
burn
) new ROM devices. During the process of developing
and debugging software, modification of the program code frequently occurs.
Consequently, an updated program must be reinstalled in the target system’s
memory. The process of preparing new ROMs is slow, and a ROM emulator with a
fast computer link provides an alternative means of updating the system memory.
NetROM is a ROM emulator product provided by a Fusion29K tool
development partner. It can emulate 8–bit, 16–bit or 32–bit wide memory devices as
required. Depending on the width (number of bits) of the memory being emulated,
between one and four cables are required to connect the NetROM to the target system
memory. Up to 1M byte of memory can be emulated, depending on the pin layout of
the memory devices in use. The 1M byte limitation does not restrict NetROM’s use
for developing programs which are larger than 1M byte –– this is achieved via the
on–board UART. The UART is mapped into a location within the emulated memory
space. The 29K processor can exchange data with the UART. The host computer can
also access the UART and hence exchange information with the 29K processor.
The MiniMON29K bundle contains a driver for the NetROM UART (often
referred to as a virtual UART). This enables the TIP program (MonTIP) running on
the host computer to communicate with the DebugCore software running on the 29K
target system. The method enables programs to be downloaded into the target
systems DRAM memory. Typically, OS–boot, the DebugCore and support drivers
are placed in emulation memory; then, via MonTIP support, programs are loaded and
executed out of the target system’s DRAM memory.
The NetROM equipment connects to the host computer via an Ethernet
connection. A NetROM can be used with an IBM PC compatible machine running
Windows; however, because of their Ethernet connection, they are much more
frequently used with networked Unix based systems. The Unix machine serving the
NetROM will have an entry in (typically) its /etc/bootptab file, specifying the IP and
Ethernet addresses allocated to the NetROM. Also specified in the bootptab file is the
the path to the NetROM configuration file. An example bootptab file entry for a
CMU type server is shown below. The actual NetROM configuration file is
/tftpboot/netrom/startup2.bat. Note, for servers running in “secure” mode, the
/tftpboot directory must be at the root of the path to the NetROM configuration file.
The NetROM (client) Ethernet hardware address is given by the “
:ha=
” field.
netrom2:hd=/tftpboot/netrom:bf=startup2.bat:sm=255.255.255.255:
ht=1:ha=00402f008444:ip=163.181.22.60
When the host server connects to the NetROM client, the configuration file is
downloaded into the NetROM. A portion of the /tftpboot/netrom/startup2.bat is