
Pin Descriptions
(Continued)
PIN DESCRIPTIONS SPECIFIC TO MICROWIRE MODE
ONLY (MW
e
1)
Pin
Symbol
No.
Li
a
Receive 2B1Q signal differential inputs
3
Li
b
from the line transformer. For normal full-
duplex operation, these pins should be
connected to the Lo
g
pins through the
recommended coupling circuit, as shown
in the Applications section.
Description
2
28
MW
The Microwire/GCI Select pin, which must
be tied to V
CC
D to enable the Microwire
Interface with any of the data formats at
the Digital System Interface.
12
BCLK
The Bit Clock pin, which determines the
data shift rate for ‘B’ and ‘D’ channel data
on the digital interface side of the device.
When Digital System Interface (DSI) Slave
mode is selected (see Digital Interfaces
section), BCLK is an input which may be
any multiple of 8 kHz from 256 kHz to
4.096 MHz. It need not be synchronous
with MCLK.
When DSI Master mode is selected, this
pin is a CMOS output clock at 256 kHz,
512 kHz, 1.536 MHz, 2.048 MHz or 2.56
MHz, depending on the selection in Com-
mand Register 1. It is synchronous with
the data on Bx and Br.
In DSI Slave mode, this pin is the Transmit
Frame Sync pulse input, requiring a posi-
tive edge to indicate the start of the active
channel time for transmit B1 channel data
into Bx. In DSI Master mode, this pin is a
Frame Sync CMOS output pulse conform-
ing with the selected Digital Interface for-
mat.
6
FSa
7
FSb
In DSI Slave mode, this pin is the Receive
Frame Sync pulse input, requiring a posi-
tive edge to indicate the start of the active
channel time of the device for receive B
channel data out from Br (see DSI Format
section). In DSI Master mode this pin is a
Frame Sync CMOS output pulse conform-
ing with the selected Digital Interface for-
mat.
13
Bx
The digital input for B and, if selected, D
channel data to be transmitted to the line;
must be synchronous with BCLK.
11
Br
The TRI-STATE output for B and, if select-
ed, D channel data received from the line;
it is synchronous with BCLK.
18
CI
The Microwire control channel data input.
19
CO
The Microwire control channel TRI-STATE
output for status information. When not
enabled by CS, this output is high-imped-
ance.
*
Crystal specifications: 15.36 MHz
g
50 ppm parallel resonant; R
S
s
20
X
.
Load with 33 pF to GND each side (
a
7 pF due to pin capacitance).
Pin
No.
Symbol
Description
17
CCLK
The Microwire control channel Clock input,
which may be asynchronous with BCLK.
27
CS
The Chip Select input, which enables the
Control channel data to be shifted in and
out when pulled low. When high, this pin
inhibits the Control interface.
26
INT
The Interrupt output, a latched open-drain
output signal which is normally high-im-
pedance, and goes low to indicate a
change of status of the loop transmission
system. This latch is cleared when the
Status Register is read by the microproc-
essor.
16
Dx
When the D-port is enabled this pin is the
digital input for D channel data to be trans-
mitted to the line clocked by DCLK or
BCLK, see Register CR2. When the D-port
is disabled via CR2, this pin must be tied to
GND.
15
Dr
When the D-port is enabled this pin is the
TRI-STATE output for D channel data to
be received from the line clocked by DCLK
or BCLK, see Register CR2.
When the D-port is enabled, in DSI Slave
or Master mode, this is a 16 kHz clock
CMOS output for D channel data. When
the D-port is disabled or not used, this pin
must be left open-circuit.
14
DCLK
PIN DESCRIPTIONS SPECIFIC TO GCI MODE ONLY
(MW
e
0)
Pin
Symbol
No.
Description
28
MW
The Microwire/GCI select input, which
must be tied to GND to enable the GCI
mode at the Digital System Interface.
27
MO
The GCI Master/Slave select input for the
clock direction. Connect this pin low to se-
lect BCLK and FSa as inputs i.e., GCI
Slave; Selection of LT or NT mode must
be made in register CR2. When MO is con-
nected high, NT Mode is automatically se-
lected, and BCLK, FSa and FSb are out-
puts, i.e., the GCI Master, see Section 8.
12
BCLK
The Bit Clock pin, which controls the shift-
ing of data on the Bx and Br pins, at a rate
of 2 BCLK cycles per data bit. When GCI
Slave mode is selected (see Digital Inter-
faces section), BCLK is an input which
may be any multiple of 16 kHz from
512 kHz to 6.144 MHz. It need not be syn-
chronous with MCLK.
When GCI Master mode is selected, this
pin is a CMOS output clock at 512 kHz or
1.536 MHz, depending on the connection
of the S2/CLS pin. It is synchronous with
the data on Bx and Br.
3