Dataman S4 Programming The 2716

The 2716 takes Vpp on pin 21, which on S4 is address line A11. Most 2716s require this pin to be held high to read. However, we cannot reconfigure A11 as a control line with S4's hardware, and as a result, 2716s will not load or verify properly in any address range where A11 is low, although they will program correctly from any address.

There are two possible solutions. One is to load the code to be programmed at address XX800 rather than address XX000, or move it there after loading, and program the device from this address; this will ensure that A11 is always held high during read operations. The other, when the code MUST be programmed from address 00000, is to clip a silicon diode (eg 1N914) into the ZIF socket with the device. The cathode (striped end) should be to pin 21, the anode to pin 24, and this again will hold pin 21 high. We recommend the first solution where possible.

When emulating 2716s, many target systems have pin 21 linked to Vcc. Although we drive this line low internally during emulation, it is possible for the target system to override the pull down, which results in the target seeing the code at address 00800 rather than 00000. Again, there are two solutions. We recommend that you copy the code from addresses 00000-007FF to address 00800 (use the MOVE command) and emulate as a 2732. This will eliminate any possibility of over dissipation within S4. The alternative is to physically cut the A11 line in the emulation lead - very much a last resort.