As far as I can make out, these are the internal registers in the 5710 custom chip: FDC - $2000-2005: With some experimentation, I have been able to verify that there are indeed six registers for the FDC. The last 2 registers, 2004-2005, appear to be configuration or mask registers for 2001-2002. These are the track and sector registers in the WD1770. By writing various values to 2004-2005, the 2001-2002 registers will return values with some of the high bits set to 1. The ROM accesses $2000-2002. CIA - $4000-400F: When read, these addresses return FF, except 400C-400E which return 00 F7 BF. The ROM reads and writes to these three addresses, so my routine may not be fast enough to see any changes (interrupt routines, etc. may reset them). These 3 locations correspond to the serial interface in the 6526. The other 13 registers of the 6526 may not exist in this chip. Unknown Interface at $4010-4017: There are 8 registers here that can be read and written. The ROM routines access the first 6 of these. The routines that use these are located at $8A6B-8EBF. In the 1571, the routines located here access the drive in CP/M mode. Do we have an IBM type disk controller here? Limitations: My search of the ROM routines would find only locations accessed by direct addressing. Any addresses using indirect addressing would not be found. I have not yet found the routines that initialize the chips. - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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