SM8213 datasheet(17/33 Pages) NPC

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SM8213AM

NIPPON PRECISION CIRCUITS—17

Decoder Set Command Transfer (CPU to SM8213AM)

In the SM8213AM, the Break, Back-up, Write, BS-

test, Start and End auxiliary modes are control sig-

nals from the CPU. These modes are set by data writ-

ten on SDI in sync with the SCK clock (see

“Data/Flags” section).

Allow a minimum of 1.67 ms after transferring each

command or data before issuing the next processing

command in write mode. In other modes, allow a

minimum of 4.0 (1.67) [0.9] ms.

When sending data from the decoder to the micro-

controller, the SCK clock frequency should not be

less than 1200 Hz when in write mode. In other

modes, the frequency should not be less than 512

(1200) [2400] Hz. If this occurs, the SCK counter is

reinitialized. This function, however, does make

restoring operation easy even if this or another clock

is accidentally input. Note that read mode function is

described in the “Decoder Internal Status Transfer”

section.

Break

This is the interrupt command to stop reception and

data transfer. When the Break command is detected,

the received code word ends and reception stops,

then the device waits for self frame address detection

or sync code detection timing. Reception may con-

tinue for up to 32-bit units of time after the Break

command is received (or 34-bit time after the Break

command is sent).

Even though message reception may continue for a

short time when the Break command is sent, sync

code detection does not take place and accordingly

the received data may be deemed to have many

errors.

Also, when CPU BREAK input interrupt end-of-

message method only is selected, message reception

continues even if an address code or an idle code is

present, as long as the Break command is not issued.

The time required from when the Break command is

issued until received data is output can be approxi-

mately 2 to 3 code words at internal sync speed. Dur-

ing this interval, 32 clock cycles are sent to the

decoder while ATTN is LOW, and processing should

be performed just as for normal operation. If no pro-

cessing is performed, subsequent operation may

become unstable.

Back-up (Power save control)

This is the decoder OFF mode command. This com-

mand stops all internal operation except the oscilla-

tor, and thus is used to control current consumption.

(the decoder internal status is write mode).

Note that in back-up mode, the input/output pins do

not become high impedance.

Back-up mode is released and operation restarts

when the decoder set start command is issued. All

parameter and address information is retained during

back-up, so operation starts directly from preamble

mode.

Write

This is the parameter and address write command.

This operation mode can also be used to modify

parameters and addresses. Write mode can be acti-

vated from BS-test mode, and also approximately 50

ms after reset, but you should allow at least 900 ms

for the oscillator internal to start and stabilize.

Parameters and addresses can be changed by ﬁrst

issuing a decoder set command to enter write mode

and then writing new parameters and addresses. Note

that in write mode, all internal operation takes place

with the same timing as for 1200 bps speed mode.

BS1, BS2 and BS3 are held LOW.

Each of the addresses can be turned ON/OFF,

according to ﬂag settings in the data written. Using

this feature for a speciﬁc address in a pager allows

the service provider, by prior agreement, to prohibit

improper use of the pager delivery service (exclud-

ing delivery testing, stopping subsidiary services and

similar functions).

In the SM8213AM, data writes from the microcon-

troller have priority, even if a received information

transmit ready signal (ATTN = LOW) is present

(forced write).

When reception from the decoder RF stage has prior-

ity, operation switches to write mode after the end-

of-message is conﬁrmed by monitoring the internal

operation using the read command. Then the param-

eter set commands and address set commands are

written.

After writing, write mode is released using the

decoder set start command, and operation starts from

preamble mode.

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