
XRT84L38
36
OCTAL T1/E1/J1 FRAMER
REV. 1.0.1
1.3
Interfacing the XRT84L38 to the Local μC/μP via the Microprocessor Interface Block
A[6:0]
I
Seven-Bit Address Bus Inputs
The XRT84L38 Framer Microprocessor Interface uses a Multiplexed Address bus. This
address bus is provided to permit the user to select an on-chip register or buffer location for
Read/Write access.
CS
I
Chip Select Input
This active-low signal selects the Microprocessor Interface of the XRT84L38 Framer and
enables Read/Write operations with the on-chip registers/buffer locations.
T
ABLE
6: I
NTEL
MODE
: M
ICROPROCESSOR
I
NTERFACE
S
IGNALS
XRT84L38
P
IN
N
AME
I
NTEL
E
QUIVALENT
P
IN
T
YPE
D
ESCRIPTION
ALE_AS
ALE
I
Address-Latch Enable:
This active-high signal is used to latch the contents on
the address bus, A[6:0]. The contents of the Address Bus are latched into the
A[6:0] inputs on the falling edge of ALE_AS. Additionally, this signal can be
used to indicate the start of a burst cycle.
RD
RD*
I
Read Signal:
This active-low input functions as the read signal from the local
μP
.
When this signal goes "Low", the Framer Microprocessor Interface places the
contents of the addressed register on the Data Bus pins, D[7:0]. The Data Bus is
tri-stated once this input signal returns "High".
WR
WR*
I
Write Signal:
This active-low input functions as the write signal from the local
μP
. The contents of the Data Bus (D[7:0]) is written into the addressed register
via A[6:0], on the rising edge of this signal.
RDY_DTAC
K
READY*
O
Ready Output:
This active-low signal is provided by the Framer and indicates
that the current read or write cycle is to be extended until this signal is asserted.
The local
μP
typically inserts WAIT states until this signal is asserted. This output
toggles "Low" when the device is ready for the next Read or Write cycle.
T
ABLE
7: M
OTOROLA
M
ODE
: M
ICROPROCESSOR
I
NTERFACE
S
IGNALS
XRT84L38
P
IN
N
AME
M
OTOROLA
E
QUIVALENT
P
IN
T
YPE
D
ESCRIPTION
ALE_AS
AS*
I
Address Strobe:
This active-low signal is used to latch the contents on the
address bus input pins, A[6:0], into the Microprocessor Interface circuitry. The
contents of the Address Bus are latched into the Framer on the rising edge of the
ALE_AS signal. This signal can also be used to indicate the start of a burst cycle.
RD
DS*
I
Data Strobe:
This signal latches the contents of the bi-directional data bus pins
into the Addressed Register within the Framer during a Write Cycle.
WR
R/W*
I
Read/Write Input:
When this pin is "High", it indicates a Read Cycle. When this
pin is "Low", it indicates a Write cycle.
RDY_DTAC
K
DTACK*
O
Data Transfer Acknowledge:
The Framer asserts DTACK in order to inform the
CPU that the present READ or WRITE cycle is nearly complete. The 68000 fam-
ily of CPUs requires this signal from its peripheral devices in order to quickly and
properly complete a READ or WRITE cycle.
T
ABLE
5: XRT84L38 M
ICROPROCESSOR
I
NTERFACE
S
IGNALS
THAT
EXHIBIT
CONSTANT
ROLES
IN
BOTH
THE
I
NTEL
AND
M
OTOROLA
M
ODES
P
IN
N
AME
T
YPE
D
ESCRIPTION