Qume DataTrak 8 Manual descarregar pdf (Página 20)

SECTION 2 HARDWARE DESCRIPTION

PCB PCA PRECOMPENSATION

OFF

200 ns.

160 ns.

120 ns.

Table 2-8. Write Precompensation

2.14 ON-BOARD TIMER

The On-Board Timer

provides both a motor

control for 5" drives and

a means for deselecting

any drive if not used for

a given period of time.

The 1791-01 will unload

the head of a drive if not

used in 15 revolutions,

but in some drives the

stepper-motor will still

consume power. The timer

is under complete control

of the onboard processor. It can be set, reset, and examined by

appropriate I/O operations. See figure 2-8.

Figure 2-8.

On-board Timer

2.15 STEP CONTROL

The STEP CONTROL circuit provides more flexible control of

the step function than the 1791-01. Step pulses are issued under

control of the on-board processor. The interval between step

pulses are timed by on-board software and can be resolved to

better than 0.10 milliseconds. The step pulse width has been set

at 3 microseconds. This appears satisfactory for most disk

drives. If needed, this value can be altered by choosing a new

value for C9 or R10. See Figure 2-9.

Figure 2-9. Step and Direction

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Qume DataTrak 8 Manual Página 20