Datasheet

SN74GTLPH1655
16-BIT LVTTL-TO-GTLP ADJUSTABLE-EDGE-RATE
UNIVERSAL BUS TRANSCEIVER
SCES294C – OCTOBER 1999 – REVISED AUGUST 2001
3–137
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
functional description
The SN74GTLPH1655 is a high-drive (100 mA), 16-bit UBT transceiver containing D-type latches and D-type
flip-flops for data-path operation in transparent, latched, or clocked modes. The device is uniquely partitioned
as two 8-bit transceivers with individual latch timing and output signals and a common clock for both transceiver
words. It can replace any of the functions shown in Table 1. Data polarity is noninverting.
Table 1. SN74GTLPH1655 UBT Transceiver Replacement Functions
FUNCTION 8 BIT 9 BIT 10 BIT 16 BIT
Transceiver ’245, ’623, ’645 ’863 ’861 ’16245, ’16623
Buffer/driver ’241, ’244, ’541 ’827 ’16241, ’16244, ’16541
Latched transceiver ’543 ’16543
Latch ’373, ’573 ’843 ’841 ’16373
Registered transceiver ’646, ’652 ’16646, ’16652
Flip-flop ’374, ’574 ’821 ’16374
SN74GTLPH1655 UBT transceiver replaces all above functions
Data flow for each word is determined by the respective latch enables (xLEAB and xLEBA), output enables
(xOEAB
and xOEBA), and clock (CLK). The output enables (1OEAB, 1OEBA, 2OEAB, and 2OEBA) control
byte 1 and byte 2 data for the A-to-B and B-to-A directions, respectively. Note that CLK is common to both
directions and both 8-bit words. OE
also is common and disables all I/O ports simultaneously.
For A-to-B data flow, the devices operate in the transparent mode when LEAB is high. When LEAB transitions
low, the A data is latched independent of CLK high or low. If LEAB is low, the A data is registered on the CLK
low-to-high transition. When OEAB
is low, the outputs are active. With OEAB high, the outputs are in the
high-impedance state.
The data flow for the B-to-A direction is identical, except OEBA
, LEBA, and CLK are used.
Function Tables
FUNCTION
†
INPUTS
OUTPUT
OEAB LEAB CLK A
B
MODE
H X X X Z Isolation
L L H X B
0
‡
L LLXB
0
§
Latched storage of A data
L H X L L
L HXH H
True transparent
L L ↑ L L
L L ↑ H H
Clocked storage of A data
†
A-to-B data flow is shown. B-to-A flow is similar, but uses OEBA
, LEBA, and
CLK. The condition when OEAB
and OEBA are both low at the same time is
not recommended.
‡
Output level before the indicated steady-state input conditions were
established, provided that CLK was high before LEAB went low
§
Output level before the indicated steady-state input conditions were
established