SM8212 datasheet(11/32 Pages) NPC

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NIPPON PRECISION CIRCUITS-11

SM8212B

3. Operating Modes

(1) Power-ON mode

After power is applied, the internal registers should be

reset using RSTN.

When ATTN goes HIGH, the decoder sends a write

request for a decoder set read command and then waits for

the microcontroller (decoder set write command timing

starts approximately 50 ms after reset, but for safety, wait

minimum 900ms when Power-ON mode). The internal

operation in write mode takes place at the same timing as

for 1200 bps speed mode.

Write data is prepared in 32-bit batches of 1 parameter

batch and 8 address data batches for a total of 9 batches.

The parameter and address set commands are processed

in sync with the decoder internal clock (1200 Hz). As a

consequence, a gap of 28.4 ms minimum should be left

between batches to provide time for processing.

Alternatively, data can be written by first using the decoder

set read command to confirm whether or not processing is

still in progress (BUSY) before writing each batch. If the

time gap is 28.4 ms or greater, confirmation (READY) is

not required.

After parameters and all addresses have been written and

after decoder processing, the decoder set start command

transfers operation from write mode and starts preamble

mode operation.

When setting parameters and addresses in write mode,

the SCK clock frequency should not be less than 1200 Hz.

If this occurs, the SCK counter is reinitialized. This func-

tion, however, does make restoring operation easy even if

this or another clock is accidentally input.

In write mode, after power is applied and after reset ini-

tialization, all 9 batches (1 parameter and 8 address batch-

es) should be set. If not all batches are set, subsequent

operation may become unstable.

BUSY

RSTN

SCK

SDI

SDO

BUSY

WRITE MODE

PREAMBLE MODE

: 8-bit unit time data

: 8-bit unit time clock

: 8-bit unit time indeterminate data

DA T

READ

READY

START

READ

DA T

: 32-bit unit time parameter/address data

READY

READ

Figure 4. Power-ON (WRITE) mode timing

Refer to the AC Characteristics section for detailed timing specifications.

max.

28.4ms

1 ms min

max 900ms

129ms max

max.

1.67ms

The SM8212B has four operating modes: Power-ON

(Write), Preamble, Idle and Lock modes.

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