MX878
Functional Description
The MX878 is an 8 channel high voltage driver
with 8-bit input control. The MX878 interfaces to a
microprocessor through a standard 3 wire serial
interface and an active low chip select, or can be
used in a parallel-in, parallel-out configuration.
Parallel data is transferred to the I/O register of
the MX878 through the parallel input pins, IN0
through IN7 on the falling edge of the chip select
pin, CS . When CS is in a logic low state, serial
data can be transferred to the I/O register through
the serial input pin, SDI, and from the I/O register
through the serial output pin, SDO. Parallel or
serial input data is transferred from the I/O
register to the latch and high voltage output
drivers, OUT0 through OUT7, on the positive
edge of CS . This data remains latched until the
next positive edge of CS .
The 8-bit I/O shift register is clocked by the
serial clock pin, SCK. Serial data presented at the
SDI pin is transferred to the shift register on the
positive edge of SCK. Data shifts out of the
register through the SDO pin on the negative
edge of SCK. SDI and SCK are ignored, and
SDO transitions to a high impedance condition
when CS is at a logic high state.
Serial data is received by the MX878 through
the SDI pin. This data is accepted on the rising
edge of SCK. A specific output is programmed to
a logic high state if SDI is at a logic high state
during the rising edge of SCK. Conversely, a
specific output is programmed to a logic low state
if SDI is at a logic low state during the rising edge
of SCK. Outputs transition to their programmed
states on the positive edge of CS if the output
enable pin, OE is in a logic high state.
The MSB input data (IN7) is presented at the
serial output pin, SDO on the falling edge of CS .
Input data from IN6 through IN0 is sequentially
presented at SDO on negative SCK transitions if
CS remains in a logic low state. If CS is at a
logic low state beyond 8 cycles of SCK, SDI data
that has propagated through the I/O register will
then be presented at SDO. The SDO pin
transitions to a high impedance state when CS
is in a logic level high state, thus allowing multiple
serial peripherals to share the microprocessor
data pin.
IXYS
Serial Data Transfer Example
IN7
IN6
IN5
IN4
IN3
IN2
IN1
IN0
SDI
CS
*
SCK
SDO
0
0
1
0
1
1
1
0
0
0
1
0
1
1
1
0
1
t1
0
0
0
0
1
1
0
SDI at
time t1
1
0
0
0
0
1
1
0
OUT7
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
OUT0
Devices may be serially cascaded by
connecting SDO to SDI of the next device. Pins
SCK and CS are common to all devices in serial
cascade. For n-cascaded devices the CS should
remain low for 8n cycles of SCK.
An output enable pin, OE enables the driver
outputs OUT0 through OUT7 when logic high. A
logic low level on OE forces the OUT0 through
OUT7 outputs to a high impedance state.
The MX878 can also operate as a parallel-in,
parallel-out level shifter and driver. SCK must
remain at a logic low state when operating in this
mode. Parallel input data presented to IN0
through IN7 is captured on the falling edge of
CS . This data is transferred to OUT0 through
OUT7 on the rising edge of CS , and remains
latched until the next rising edge of CS .
MX878
Drawing No. 087809
6
06/08/06
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IXYS [ IXYS CORPORATION ]
