lpc47s457-ns Standard Microsystems Corp., lpc47s457-ns Datasheet - Page 32

• Manufacturer Part Number: lpc47s457-ns
• Description: Advanced I/o With X-bus Interface
• Manufacturer: Standard Microsystems Corp.

Tape Drive Register (TDR)
Address 3F3 READ/WRITE
The Tape Drive Register (TDR) is included for 82077 software compatibility and allows the user to assign tape
support to a particular drive during initialization. Any future references to that drive automatically invokes tape
support. The TDR Tape Select bits TDR.[1:0] determine the tape drive number. Table 5 illustrates the Tape Select
Bit encoding. Note that drive 0 is the boot device and cannot be assigned tape support. The remaining Tape Drive
Register bits TDR.[7:2] are tristated when read. The TDR is unaffected by a software reset.
Normal Floppy Mode
Normal mode. Register 3F3 contains only bits 0 and 1. When this register is read, bits 2 - 7 are ‘0’.
Enhanced Floppy Mode 2 (OS2)
Register 3F3 for Enhanced Floppy Mode 2 operation.
SMSC DS – LPC47S45x
REG 3F3
REG 3F3 Reserved Reserved
Bit 5
Bit 5
X
X
1
0
1
0
DIGITAL OUTPUT
DIGITAL OUTPUT
DB7
DB7
Bit 4
Bit 4
REGISTER
REGISTER
0
X
X
1
0
1
0
Table 4 − Internal 2 Drive Decode - Drives 0 and 1 Swapped
TAPE SEL1
(TDR.1)
Bit1
Bit1
X
X
0
0
0
0
0
0
1
1
DB6
DB6
0
Table 3 − Internal 2 Drive Decode - Normal
Bit 0
Bit 0
X
X
0
1
0
1
DRIVE SELECT OUTPUTS
DRIVE SELECT OUTPUTS
DB5
DB5
DATASHEET
Table 5 − Tape Select Bits
Drive Type ID
0
TAPE SEL0
nDS1
nDS1
(TDR.0)
1
0
1
0
1
1
(ACTIVE LOW)
(ACTIVE LOW)
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0
1
0
1
DB4
DB4
0
nDS0
nDS0
0
1
1
1
0
1
Floppy Boot Drive
DB3
DB3
DRIVE SELECTED
0
None
MOTOR ON OUTPUTS
MOTOR ON OUTPUTS
nMTR1
nMTR1
nBIT 5
nBIT 5
nBIT 5
nBIT 4
nBIT 4
nBIT 4
1
2
3
DB2
DB2
(ACTIVE LOW)
(ACTIVE LOW)
0
tape sel1
tape sel1
DB1
DB1
nMTR0
nMTR0
nBIT 4
nBIT 4
nBIT 4
nBIT 5
nBIT 5
nBIT 5
tape sel0
tape sel0
DB0
DB0
Rev. 04-30-07