Zenith H-100 Service Manual page 57

H-207 FLOPPY DISK CONTROLLER BOARD DEFINITIONS
5-141
AO-A7
ALE
BDSEL
Address bits.
Address latch enable. Data and address lines
from the CPU have val id information.
Board select. The H-207 board is selected
(enabled) •
CLK Clock signal.
CS Chip select. When asserted, the 1797 chip is
enabled.
D~-D7
DDEN
D1Y"-D17
DrR
000-007
DRQ
Data bits on the H-207 board's internal data bus.
Double density enable.
Data-in bits on the S-100 bus ("in" with respect
to the CPU, not the Controller).
Direction of drive head. When high, the drive
head is stepping in. When low, the drive head
is stepping out.
Data-out bits on the S-100 bus ("out" with respect
to the CPU, not the Controller).
Data request. The 1797 data register needs data
for write operations or the register has data
for read operations.
DSA Drive select A. Used with DSB to address the
drives.
DSB Dr i v e select B. Used wi th DSA to address the
drives.
EARLY
Write data bit early to disk drive (used for
precompensation).
10-82
HLD Head load.