Specifications

ATAPI For Streaming Tape QIC-157 Rev B
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3.6. ATAPI Register Map (Packet Command)
Logic conventions are: A = signal asserted, N = signal negated, x = does not matter
Table 3-2 I/O Port Functions/Selection Addresses (Compatibility Model)
Addresses Functions
CS1FX CS3FX DA2 DA1 DA0 Read (DIOR-) Write (DIOW-)
Control Block Registers
N A 0 0 0 Floppy A Status Unused
N A 0 0 1 Floppy B Status Unused
N A 0 1 0 Unused Floppy Digital Output Register
N A 0 1 1 Floppy ID / Tape Control RESERVED
N A 1 0 0 Floppy Controller Status RESERVED
N A 1 0 1 Floppy Data Register
N A 1 1 0 Alternate ATAPI Status Drive Control
N A 1 1 1 Diskette Change/Drive Address Not Used
Command Block Registers
A N 0 0 0 Data
A N 0 0 1 ATAPI Error Register ATAPI Features
A N 0 1 0 ATAPI Interrupt Reason Register
A N 0 1 1 Reserved For SAM TAG Byte
A N 1 0 0 ATAPI Byte Count Register (bits 0-7)
A N 1 0 1 ATAPI Byte Count Register (bits 8-15)
A N 1 1 0 Drive Select
A N 1 1 1 ATAPI Status ATA Command
Except for the Data Register, all the ATAPI registers are referenced using Byte (8 Bit) Read and
Writes. The Data Register is ALWAYS referenced as a 16 bit word.
The following table is shown for reference only. No word references to the registers (Other than the
data register) are allowed by this specification.
Table 3-3 Word Mapping of Task File Registers
Typical
Addr
Functions
Read (DIOR-) Write (DIOW-)
Control Block Registers
3x0 Floppy B Status Floppy A Status Unused Unused
3x2 Floppy ID / Tape Control Unused Reserved Floppy Digital Output
3x4 Floppy Data Register Floppy Controller Status Floppy Data Register Reserved
3x6 Change/Drive Address Alternate ATAPI Status Unused ATAPI Device Control
Command Block Registers
1x0 Data Register Data Register
1 ATAPI Error Register ATAPI Feature Register
1x2 Reserved for SAM Tag ATAPI Interrupt Reason Reserved for SAM Tag Sector Count
1x4 ATAPI Byte Count Register ATAPI Byte Count Register
1x6 ATAPI Status Drive Select Register ATA Command Register Drive Select Register