e7804 Semtech Corporation, e7804 Datasheet - Page 10

• Manufacturer Part Number: e7804
• Description: 133 Mhz Quad Pin Electronics Driver And Window Comparator
• Manufacturer: Semtech Corporation

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Read/Write: 1 bit
This determines whether a particular address/function is
being written or read. (Note that some functions are read-
only or write-only).
Function: 4 bits
This determines which function within a channel or set is
being set or read.
Refer to Figure 2 for a block diagram of the Write and Read
logic for the serial programming. The serial data is input
into the device SDIN pin. The data at SDIN is clocked in on
the high-going edge of the CLKIN input signal. The data at
the SDOUT pin is clocked out on the low-going edge of the
CLKIN input signal for ease of “daisy chaining” multiple
devices.
RESET*
There is a single input pin to the entire E7804 chip that will
clear all on-chip registers and open all on-chip switches.
This input pin, RESET*, is active low and is asynchronous,
not requiring any CLKIN transitions to operate. It is advised
that, upon power-up in a system, this pin is either held low
or cycled low for a brief time while the system and power
TEST AND MEASUREMENT PRODUCTS
Circuit Description (continued)
2007 Semtech Corp. / Rev. 7, 02/26/07
0 = write a control/data register
 = read back the contents of a register
RESET*
CLKIN
LOAD
SDIN
Figure 2. Block Diagram of Read and Write Shift Registers
SIN
D[20:24]
CK
DATA
13
24-Bit Shift Register
24-Bit Shift Register
RESET
RESET
RESET
D[5:17]
READBACK
LATCH
WRITE
0
DATA
ADR
Q
10
24
supplies become stable in order to put the E7804 into a
known starting state. After power-up, the RESET* may be
exercised or a soft reset instruction may be programmed.
Write Serial Data
Data is shifted into the WRITE shift register using CLKIN.
The data stored in the shift register will be stored into
the E7804 by asserting the LOAD input signal during
the 24th CLKIN high-going edge. The LATCH will hold the
instruction inside the E7804 for address decoding and
data storage into the appropriate on-chip registers. Seven
(7) more CLKIN high-going edges should be given
after a LOAD for full decode and all instruction
executions.
Refer to Figure 3 for a timing diagram of the writing
operation. Notice that the SDOUT data that is clocked out
on the low-going edge of CLKIN is a bit for bit representation
of the data that had been shifted into the E7804 24
clock edges beforehand. This echoing of the data allows
the user to “daisy chain” multiple E7804 devices to
minimize the number of serial data streams that need to
be implemented. The compromise is the length of time it
takes to clock through all the 24-bit instructions for all the
devices in the chain.
D[0:4]
READBIT
Read Bit Only True
"Don't Care"
SOUT – READ
SOUT – WRITE
for 24 Clocks
SDOUT
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E7804