Programming Considerations - NEC Advanced Personal Computer System Reference Manual

Controller PCB
3-24
Figure 3-12 is a timing diagram that defines the timing of this three-phase command
process.
PROCESSOR
COMMAND
PHASE
EXECUTION
PHASE
RESULT
PHASE
r .... - _ _ .A _ _ _ ,
~ ~
DATA SEND
DATA SEND
+
I
DA T A RECEIVE
•
I
DlO
- - - + - - - - - 1 1 - - - - - '
L
RQM
FDC DATA
RECEIVE
I
DATA
RECEIVE
DATA
SEND
Figure 3-12 FDC Timing Diagram
3.4.1 Programming Considerations
Table 3-8 defines the symbols used in the FDC command summary given in Table
3-9. Tables 3-10, 3-11, 3-12 and 3-13 define the bit functions of the command status
registers. Table 3-14 lists the 110 addresses and functions of the FDC registers.
Table 3-8 FDC Symbols
SYMBOL NAME
DESCRIPTION
AO Address Line 0 Controls the selection of the Main Status
Register (AO=O) or Data Register
(AO=l).
C Cylinder Number Specifies the selected cylinder number.
D Data Specifies the data pattern that is going to
be written into a sector.
D7 to DO Data Bus 8-bit Data Bus, where D7 is the most
significant bit, and DO is the least
significant bit.
DTL Data Length When N is defined as 00, DTL is the
data length that users are going to read
out or write into the sector.
EOT
End of Track Indicates the final sector number on a
cylinder.