How Does the BCR Register Interaction With Internal State Machines in GPIB ASICsHardware: GPIB
Problem: I am using the NAT9914 GPIB Talker/Listener chip. I noticed that the BCR (Bit Control Register) can be used to set certain bits on the GPIB. How does this affect the internal state machines of the 9914? Will the BCR override them? Solution: The BCR is independent of anything else in the 9914. Setting a bit in the BCR immediately asserts the corresponding internal signal. There is no negotiation between the BCR and the internal state machines. However, in the NAT9914 the transceivers must be in the proper state to assert a given signal on the bus. Since the transceivers are external to the 9914, they are configured by some control signals from the 9914. For example, when you are a talker you don't drive NRFD, it's an input. When you are a listener you do drive NRFD, it's an output. The NAT9914 will automatically configure the transceivers to drive or not drive. The TNT4882 and TNT5002/4 will assert a signal from the BCR regardless of what state they are in. This is because they have integrated transceivers and can simultaneously drive and read the GPIB signals. Related Links: Attachments:
Report Date: 04/29/2004 Last Updated: 05/04/2004 Document ID: 38SAI3V4 |
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