Tandy 6000 HD, Service Manual

Page: 208 / 416

Service Manual
TANDY 6000/6000-HD
T A N D Y COMPUTER PRODUCTS ----------------------------------------------------------------------
7.10 Hard Disk Controller
7.10.1 System Overview
The Tandy 6000 with built in hard disk is identical to the
standard 6000, except for the additional 15-meg HD drive,
identical to the standard 16B (Cat. No. 26-6004), except for
the addition of a 15-megabyte (formatted) hard disk drive,
controller PC board, drive power supply, and associated
cables. The drive is mounted next to the existing floppy
drive in place of a second internal floppy. The power
supply for the hard disk is mounted to the outside of the
drive mounting tower. The controller PC board is located in
the bottom slot of the card cage. There are two cables
connecting the controller and the internal hard drive.
There are also connectors on the controller for adding a
secondary, external hard drive. The extra power supply is
used to power the internal hard drive and a small cooling
fan located under the drive tower. The controller PC board
is powered from the main card cage.
7.10.2 Hard Drive Controller Board
The hard drive controller (HDC) board is a two sided PC
board with the same form and size as those used in the Model
II and Model 16. This board is designed to provide all
control and data signals for connecting one internal and one
external 5.25" Winchester technology drives.
1. Host System Interface
The HDC is connected to the 6000 motherboard via an
80-position card edge connector, Jl. Data lines are passed
through an AMD 8303 inverting transceiver, U39. Eight
address lines are buffered by a 741S240, U 4 0 . Most control
signals are buffered by another 741S240, U41. This board
uses the Z80 interrupt priority daisy chain, so the board
must be placed in either the bottom card slot, or the next
one up, if the system also has an Arcnet board installed.
2. Port Decoding
The HDC uses a range of 16 consecutive eight bit port
locations with the standard range being CO to CF. Decoding
of the correct range is done by U33, a 74S138 using the
upper 4 address lines and Ml and IORQ*. A 4 position jumper
enables changing of the range to be recognized. For normal
use, the jumper should be installed between El and E 2 . See
the following table for other configurations.
- 219 -