Octal bus transceiver/register; 3-state
Rev. 03 — 15 March 2010
Product data sheet
1. General description
The 74ABT646A high-performance BiCMOS device combines low static and dynamic
power dissipation with high speed and high output drive.
The 74ABT646A transceiver/register consists of bus transceiver circuits with 3-state
outputs, D-type ﬂip-ﬂops, and control circuitry arranged for multiplexed transmission of
data directly from the input bus or the internal registers. Data on the A bus or B bus will be
clocked into the registers as the appropriate clock pin (CPAB or CPBA) goes HIGH.
Output Enable (OE) and Direction (DIR) pins are provided to control the transceiver
function. In the transceiver mode, data present at the high-impedance port may be stored
in either the A or B register or both.
The Select (SAB, SBA) pins determine whether data is stored or transferred through the
device in real-time. The DIR pin determines which bus receives data when OE is active
(LOW). In isolation mode (OE = HIGH), data from bus A may be stored in the B register
and/or data from bus B may be stored in the A register. When an output function is
disabled, the input function is still enabled and may be used to store and transmit data.
Only one of the two buses, A or B, may be driven at a time. The examples in Figure 5
“Real time bus transfer and storage” on page 6 demonstrate the four fundamental bus
management functions that can be performed with the 74ABT646A.
2. Features and beneﬁts
I Combines 74ABT245 and 74ABT373A type functions in one device
I Independent registers for A and B buses
I Multiplexed real-time and stored data
I Live insertion and extraction permitted
I Output capability: +64 mA to −32 mA
I Power-up 3-state
I Power-up reset
I Latch-up protection exceeds 500 mA per JESD78B class II level A
I ESD protection:
N HBM JESD22-A114F exceeds 2000 V
N MM JESD22-A115-A exceeds 200 V