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Messenger: Difference between revisions
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Add link to schematic and equations
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The Messenger ROM and RAM is paged out by writing to port 0x77, and paged in by reading from port 0x77. More precisely, paging is triggered by I/O to ports where A7=0, A4=1, A3=0, and A1=1, i.e. (port & 0x009a) == 0x0012. It is also paged in automatically upon execution of addresses 0x0066 and 0x0067. The serial port is accessible through most significant bit of port 0xff6f, for both sending and receiving. More precisely, the serial port is accessed through I/O ports where A7=0, A4=0, A3=1 and A1=1, i.e. (port & 0x209a) == 0x000a. Serial port I/O can be accessed regardless of whether the ROM and RAM are paged in. | The Messenger ROM and RAM is paged out by writing to port 0x77, and paged in by reading from port 0x77. More precisely, paging is triggered by I/O to ports where A7=0, A4=1, A3=0, and A1=1, i.e. (port & 0x009a) == 0x0012. It is also paged in automatically upon execution of addresses 0x0066 and 0x0067. The serial port is accessible through most significant bit of port 0xff6f, for both sending and receiving. More precisely, the serial port is accessed through I/O ports where A7=0, A4=0, A3=1 and A1=1, i.e. (port & 0x209a) == 0x000a. Serial port I/O can be accessed regardless of whether the ROM and RAM are paged in. | ||
Miguel Angel Rodríguez Jódar [http://www.zxprojects.com/images/stories/messenger_sam_coupe/messenger_interface_sam_coupe.png] has produced a schematic of the interface, and has worked with Velesoft to produce a [http://velesoft.speccy.cz/other/messenger_gal16v8%28beta5%29.zip JEDEC file with equations for the Messenger's GAL]. | |||
== Programs with Messenger snapshots support == | == Programs with Messenger snapshots support == | ||