The In Circuit Emulator Board (ICE)

Acorn System In Circuit Emulator

"The In Circuit Emulator (ICE) allows an Acorn system to connect to a second micro-processor target system by way of its 6502 processor socket. Once established this connection may be used to test hardware and to evaluate software in the target system. The ICE will be most useful in the development of new 6502 based products and in the test and repair of existing equipment.

The ICE hardware is carried on a single Eurocard (100 x 160mm) which connects to the standard Acorn system bus. A 40-way flat ribbon cable plugs on to the front of this card and provides connection to the 40-way dual-in-line plug for the target processor socket. In operation the ICE re-locates any two blocks in the target system to appear as blocks A and B in the host system. The selection of the two blocks is achieved by writing to the ICE control register which is a latch on the ICE card. After setting the control register any read or write operations by the host system into its blocks A or B are sent down the ICE cable into the target system. In this way the target system hardware may be accessed for testing with the same bus timing as would appear from its own processor. As the block selection is under software control programs for testing the target hardware can dynamically relocate the ICE allowing the whole of the target memory map to be tested.

When developing software in the host system for eventual use in the target system it will be necessary to define the machine addresses as those in blocks A or B. After proving the program these addresses must be changed to their real values before blowing the program into Read Only Memory and fitting it and the 6502 to the target system.

Also on the ICE card is a single byte register which may be read by the host system.

The bits in this register indicate the state of various pins around the 6502 socket in the target system including the +5 volt rail and the 1MHz clock."






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