Talk:Suspension Chamber 2000

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Possible Error in Specification

According to the description of GET_STATUS (A=0), the C register is set to 1 if the device is ready to trigger. However, in TRIGGER_DEVICE (A=2), it says that it triggers the device if register C is 0. Is this an error in the specification, or am I missing something?

Or, is it an intentional mistake, similar to the big-endianness of the device?

EternityCoder‎

I don't think this is a mistake. In GET_STATUS, the C register is an output from the sleep cell to the DCPU. In TRIGGER_DEVICE, the C register is an input instead.

It just means that if you check the status of the sleep cell first, you have to clear C again before triggering it.

Musashiaharon‎

Oh, I had thought, from the wording "Performs GET_STATUS, and if C is zero..." that it meant it would trigger if C was zero based on the result of GET_STATUS. I think you're right though.

EternityCoder‎

Actually, I was just working on an emulator, and, when reviewing the spec, it says that it performs GET_STATUS, which means C becomes 1. A CPU has no notion of input or output. Just because C was used in an output in GET_STATUS, doesn't mean the device can't use it as an input also. It's set as an output by GET_STATUS, and it's used as an input for TRIGGER_DEVIC.