Service Manual
TANDY 6000/6000-HD
TAN D Y COMPUTER PRODUCTS ----------------------------------------------------------------------
Write protection for the memory outside a user's partition
is provided.
Accesses outside of the user's defined
partition result in the generation of a bus error exception.
An interrupt can also be generated if the interrupt
controller is properly initialized.
There are two things that cause the generation of a bus
e r r o r :
The user addresses outside his partition
A bus time-out occurs
A bus time-out results when nonexistent memory or I/O
accesses are attempted.
The source of the bus error can be
determined by reading the status register of the interrupt
controller.
The hardware that accomplishes the memory management
function works as described in the following paragraphs.
The MC68000 processor address bits A12 through Al9 are added
to the 8-bit value that is stored in the active offset
register.
The result of this addition is the effective
address that is presented to the address bus.
The effective address is compared to the 8-bit value that is
stored in the active limit register.
If the effective
address is larger than the contents of the active limit
register, or if the addition results in a carry overflow
from the adder, a bus error is generated.
The MC68000 processor address A23 determines which set of
offset and limit registers are used.
If A23 is high, then
offset and limit registers two will be active.
If A23 is
low, then offset and limit registers one will be active.
Each of the two extents is implemented with an offset
register and a limit register, which are 74LS374 8-bit
D-type registers.
The 8-bit value in the offset register is
added to the eight processor address lines (KA12 to KA19) to
form User Extent Address lines (UEA12 to UEA19).
The effective address is then compared with the value in the
limit register.
If the EA is greater than the limit, an
out-of-bounds error is generated.
A carry out of the adder (2F83) also generates an OBERROR.
If OBERROR occurs when MMA and GAS are active, then an
Address Error is generated (ADERR).
This signal (ADERR) is
one of the interrupt sources.
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Summary of Contents for 6000 HD
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Page 124: ...Service Manual TANDY 6000 6000 HD TANDY COMPUTER PRODUCTS Table 7 5 Input Output Port Map 125...
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Page 266: ...FIGURE 1 1 DISK DRIVE...
Page 268: ...2 2...
Page 279: ...FIGURE 3 2 CONTROL AND DATA TIMING REQUIREMENTS 3 7...
Page 283: ...FIGURE 3 3 LSI CIRCUIT BOARD ASSEMBLY 3 11...
Page 289: ...FIGURE 3 5 DISKETTE CARE AND HANDLING 3 17...
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Page 294: ...FIGURE 4 4 INTERCONNECT BLOCK DIAGRAM 4 4...
Page 295: ...FIGURE 4 6 TRACK O TIMING 4 5...
Page 304: ...FIGURE 5 2 TIMING DISK FIGURE 5 3 HUB CENTER LINE AND TRACK LOCATION 5 4...
Page 337: ...FIGURE 6 19 HEAD CARRIAGE 6 25...
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Page 373: ...FIGURE 3 5 RADIAL CONFIGURATION 3 7...
Page 374: ...FIGURE 3 6 DAISY CHAIN CONTROL LINES...
Page 382: ...FIGURE 3 11 RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 1...
Page 383: ...FIGURE 3 11 CONTINUED RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 1 3 17...
Page 384: ...FIGURE 3 12 RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 2 3 18...
Page 385: ...FIGURE 3 13 RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 3 3 19...
Page 386: ...FIGURE 3 13 CONTINUED RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 3 3 20...
Page 387: ...FIGURE 3 14 LOAD GRAPH 3 21...
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Page 390: ...FIGURE 4 1 TEST POINT LOCATIONS...
Page 394: ...o FIGURE 4 3 READ DATA WAVEFORMS 15 TPR AND 14 TPR o 4 6...
Page 397: ...FIGURE 4 4 INDEX SENSOR 4 9...
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