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LTC1292/LTC1297

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LTC1292 Operating Sequence

I FOR ATIO

Motorola SPI (MC68HC11)

The MC68HC11 has been chosen as an example of an MPU

with a dedicated serial port. This MPU transfers data MSB

first and in 8-bit increments. A dummy D

word sent to the

data register starts the SPI process. With two 8-bit transfers,

the A/D result is read into the MPU (Figure 1). For the

LTC1292 the first 8-bit transfer clocks B11 through B8 of

the A/D conversion result into the processor. The second

8-bit transfer clocks the remaining bits B7 through B0 into

Microprocessor Interfaces

The LTC1292/LTC1297 can interface directly (without

external hardware) to most popular microprocessors’

(MPU) synchronous serial formats (see Table 1). If an

MPU without a dedicated serial port is used, then three of

the MPU’s parallel port lines can be programmed to form

the serial link to the LTC1292/LTC1297. Included here are

one serial interface example and one example showing a

parallel port programmed to form the serial interface.

Figure 1. Data Exchange Between LTC1292 and MC68HC11

CLK

CYC

B11

B10B9B8

B5B4

B0B1B2

B5B6

B9B10

B11

CONV

OUT

Hi-Z

SMPL

LTC1292/7 AI01

LTC1297 Operating Sequence

CLK

OUT

MPU

RECEIVED WORD

LTC1292/7 F01

B5 B4

B3 B2

B10

B11

BYTE 2

B10 B9

B8B11

1ST TRANSFER

2ND TRANSFER

BYTE 1

B2 B1

B3B4

CLK

CYC

B11