Mike_Z
Veteran Member
I am building a 8272 based FDC board for my 8080A computer. I want to be able to load CP/M 2.2, which I have the DRI license. The last few days I have been reading the DRI CP/M Operating Manual with respect to the cold start loader and the CBIOS. My questions are about the 8272 commands and the CBIOS calls. Seems that the CP/M jump table will only a few of the 8272 commands.
CP/M Jump HOME could use the 8272 Recalibrate, or the Seek commands (probably the seek).
CP/M Jump SELDDSK, Jump SETTRK, Jump SETSEC & Jump SETDMA would only set data for 8272 Seek, Read or Write
CP/M Jump READ would do a 8272 read
CP/M jump write would do a 8272 write.
The 8272 specify and recalibrate commands would be used in initialization.
The 8272 Sense drive status would be used to poll the 8272 prior to reading or writing to the MSR.
The remaining 8272 commands would not be used at all. Although I'm not sure about Sense interrupt status.
I'm guessing that the Cold Starter would need some rudimentary seek and read routines that would be stored in ROM on the computer. The CBIOS would then have these and the other 8272 commands which would be loaded from the disk. Am I correct in my thinking?
How does CP/M format a disk? Does it just use the write command, rather than the 8272 format a track command?
Mike
CP/M Jump HOME could use the 8272 Recalibrate, or the Seek commands (probably the seek).
CP/M Jump SELDDSK, Jump SETTRK, Jump SETSEC & Jump SETDMA would only set data for 8272 Seek, Read or Write
CP/M Jump READ would do a 8272 read
CP/M jump write would do a 8272 write.
The 8272 specify and recalibrate commands would be used in initialization.
The 8272 Sense drive status would be used to poll the 8272 prior to reading or writing to the MSR.
The remaining 8272 commands would not be used at all. Although I'm not sure about Sense interrupt status.
I'm guessing that the Cold Starter would need some rudimentary seek and read routines that would be stored in ROM on the computer. The CBIOS would then have these and the other 8272 commands which would be loaded from the disk. Am I correct in my thinking?
How does CP/M format a disk? Does it just use the write command, rather than the 8272 format a track command?
Mike