MM54HC646/MM74HC646 Non-Inverting
Octal Bus Transceiver/Registers
MM54HC648/MM74HC648
Inverting Octal Bus Transceiver/Registers
General Description
These transceivers utilize advanced silicon-gate CMOS
technology, and contain two sets of TRI-STATEé outputs,
two sets of D-type flip-flops, and control circuitry designed
for high speed multiplexed transmission of data.
Six control inputs enable this device to be used as a latched
transceiver, unlatched transceiver, or a combination of both.
As a latched transceiver, data from one bus is stored for
later retrieval by the other bus. Alternately real time bus
data (unlatched) may be directly transferred from one bus to
another.
Circuit operation is determined by the G, DIR, CAB, CBA,
SAB, SBA control inputs. The enable input, G, controls
whether any bus outputs are enabled. The direction control,
DIR, determines which bus is enabled, and hence the direction
data flows: The SAB, SBA inputs control whether the
latched data (stored in D type flip flops), or the bus data
(from other bus input pins) is transferred. Each set of flipflops
has its own clock CAB, and CBA, for storing data. Data
is latched on the rising edge of the clock.
Each output can drive up to 15 low power Schottky TTL
loads. These devices are functionally and pin compatible to
their LS-TTL counterparts. All inputs are protected from
damage due to static discharge by diodes to VCC and
ground.