Manuel Bilderbeek
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2008-11-27
Quite some Sony machines have hardware pause. Examples are the Sony HB-201P, HB-101P, and some more
The service manual of the 101/201 explains how it works exactly, in section 3-1. Quickly typed over for reference:
/BUSRQ is one of the Z80 CPU control signals. When /BUSRQ goes low, the CPU sets all the data/address bus signals, /MREQ, /IORQ, /RD and /WR in the high impedance state after terminating the current instruction execution. The CPU then stops the operations, and causes /BUSAK to go low to inform control that the buses have been opened.
/BUSRQ is not used in the MSX specification, but it is used to implement the pause function in the HB-101P/201P specifictation.
The rest you can better read from the image I supplied with this RFE.