Qume DataTrak 8 Manual descargar pdf (Pagina 19)

SECTION 2 HARDWARE DESCRIPTION

2.13 BOARD LEVEL COMMAND PORT

The Board Level Command Port is a parallel output port of the

on-board processor. It is used to select various

parameters as listed in Table 2-6. See Figure 2-7 for circuit

details.

DATA

BIT

SIGNAL

NAME

DESCRIPTION

DSA

DSB

DSE

SERO

DDEN

SID1

PCA

PCB

Drive select bit A 2**0.

Drive select bit B 2**1

Drive select enable

EIA signal output control

Double density enable

Side and direction select

Precomp select A

Precomp select B

Table 2-6. Command Port Bits

The signals DSA and DSB are used

to determine which drive is

selected. DSE must be asserted for

drive selection to take place. DSE

is also used to enable the on-board

processor to accept an interrupt

from the 1791-01. See Table 2-7 for

drive selection.

Double Density operation is

enabled when DDEN is set high. A low

SERO signal corresponds with a

negative EIA output.

DSE DSB DSA DRIVE

NONE

Table 2-7.

Drive Selection

SID1 serves a dual function. When using double-sided drives

and performing any type of read or write operation, this signal

selects which side of the diskette is used. A low SID1 selects

the same side as used on single-sided drives. When stepping

operations are being performed, SID1 functions as the direction

select, a low SID1 will cause stepping operations to move the

head toward track 0 (most drives) .

Precompensation is controlled by signals PCA and PCB. These

two signals allow precompensation to be enabled and at different

three levels of intensity. Table 2-8 lists this function.

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 46 47

Double D 1
. ERRATIC DISK OPERATION 4

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