SM8213 datasheet(11/33 Pages) NPC

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SM8213AM

NIPPON PRECISION CIRCUITS—11

Operating Modes

The SM8213AM has four operating modes—Power-

ON (Write), Preamble, Idle and Lock modes.

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 com-

mand timing starts approximately 50 ms after reset,

but you should allow at least 900 ms for the oscilla-

tor internal to start and stabilize). The internal opera-

tion 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 parame-

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

batches.

Ensure that there are not multiple writes requests to

turn ON the same address. Also, allow a minimum of

1.67 ms after transferring each command or data

before issuing the next processing command.

The parameter and address set commands are pro-

cessed 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 rein-

itialized. This function, however, does make restor-

ing operation easy even if this or another clock is

accidentally input.

In write mode, after power is applied and after reset

initialization, all 9 batches (1 parameter and 8

address batches) should be set. If not all batches are

set, subsequent operation may become unstable.

Figure 4. Power-ON mode timing

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

Refer to the AC Characteristics section for detailed timing specifications.

max.

28.4ms

1 ms min

max 900ms

129ms max

max.

1.67ms

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