LTC1090CJ View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1090CJ' PDF : 28 Pages View PDF
LTC1090
APPLICATIO S I FOR ATIO
Parallel Port Microprocessors
When interfacing the LTC1090 to an MPU which has a
parallel port, the serial signals are created on the port with
software. Three MPU port lines are programmed to create
the CS, SCLK and DIN signals for the LTC1090. A fourth
port line reads the DOUT line. An example is made of the
Intel 8051/8052/80C252 family.
Intel 8051
To interface to the 8051, the LTC1090 is programmed for
MSB first format and 10-bit word length. The 8051 gener-
ates CS, SCLK and DIN on three port lines and reads DOUT
on the fourth.
Hardware and Software Interface to Intel 8051 Processor
LTC1090
DOUT
8051
P1.1
ANALOG
INPUTS
DIN
P1.2
SCLK
P1.3
CS
P1.4
ACLK
ALE
DOUT from LTC1090 stored in 8051 RAM
MSB*
R2
B9 B8 B7 B6 B5 B4 B3 B2
LSB
R3
B1 B0 0 0 0 0 0 0
*B9 is MSB in unipolar or sign bit in bipolar
8051 Code
MNEMONIC
DESCRIPTION
MOV PI,#02H
CLR P1.3
SETB P1.4
CONTINUE: MOV A,#0DH
LOOP:
DELAY:
CLR P1.4
MOV R4,#08
NOP
MOV C, P1.1
RLC A
MOV P1.2, C
SETB P1.3
CLR P1.3
DJNZ R4, LOOP
MOV R2, A
MOV C, P1.1
CLR A
RLC A
SETB P1.3
CLR P1.3
MOV C, P1.1
RRC A
RRC A
MOV R3, A
SETB P1.3
CLR P1.3
SETB P1.4
MOV R5,#07H
DJNZ R5, DELAY
AJMP CONTINUE
Initialize port 1 (bit 1 is made
an input)
SCLK goes low
CS goes high
DIN word for the LTC1090 is
placed in ACC.
CS goes low
Load counter
Delay for deglitcher
Read data bit into carry
Rotate data bit into ACC
Output DIN bit to LTC1090
SCLK goes high
SCLK goes low
Next bit
Store MSBs in R2
Read data bit into carry
CIear ACC
Rotate data bit into ACC
SCLK goes high
SCLK goes low
Read data bit into carry
Rotate right into ACC
Rotate right into ACC
Store LSBs in R3
SCLK goes high
SCLK goes low
CS goes high
Load counter
Delay for LTC1090 to perform
conversion
Repeat program
210
OUTPUT PORT
3
SERIAL DATA
3
MPU
CS
LTC1090
3
CS
LTC1090
3-WIRE SERIAL
INTERFACE TO OTHER
3
PERIPHERALS OR LTC1090s
CS
LTC1090
8 CHANNELS
8 CHANNELS
8 CHANNELS
LTC1090 • AI14
Figure 5. Several LTC1090’s Sharing One 3-Wire Serial Interface
1090fc
17
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