
UM008101-0601 Direct Memory Access
the routine is being executed. Near the end of the routine, the CPU writes
an ENABLE INTERRUPTS command to the DIVA, which enables it to
generate a new interrupt.
This command is less extensive than the RESET AND DISABLE INTER-
RUPTS command because it does not reset the Interrupt Pending (IP) and
Interrupt Under Service (IUS) latches.
Figure 46. Write Register 6 Group
D7 D6 D5 D4 D3 D2 D1 D0
Base Register Byte
01
111
=C3=Reset
000
Hex Command Name
01
=C7=ResetPortATiming
001
01
=C8=ResetPortBTiming
010
01
= CF = Load
011
01
= D3 = Continue
100
10
= AF = Disable Interrupts
011
10
= AB = Enable Interrupts
010
10
= A3 = Reset and Disable Interrupts
000
10
= B7 = Enable after RETI
101
10
= BF = Read Status Byte
111
00
= 8B = Reinitialize Status Byte
010
10
= A7 = Initialize Read Sequence
001
10
= B3 = Force Ready
100
00
=87=EnableDMA
001
00
= 83 = Disable DMA
000
10
= BB = Read Mask Follows
110
Read Mask (1=Enable)
Status Byte
Byte Counter (Low Byte)
Byte Counter (High Byte)
Port A Address (Low Byte)
Port B Address (High Byte)
0
Port B Address (Low Byte)
Port A Address (High Byte)
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