PCA88021 datasheet(14/34 Pages) NXP

14 / 34 page

PCA8802_1

Product data sheet

Rev. 01 — 19 February 2009

14 of 34

NXP Semiconductors

PCA8802

Smartcard RTC

9.6 Instructions

9.6.1 Instruction set

[1]

Read of the counter is implicit with an interface read.

9.6.2 Instruction wrt_cmd

The write instruction (wrt_cmd) precedes each write sequence. Details of the writing

protocol can be found in Section 9.5.1.1.

9.6.3 Instruction dvs_cmd

The divider switch instruction (dvs_cmd) can be used to freeze the divider chain and to

put it in a deﬁned state. The ﬁrst two bits of the divider chain can not be inﬂuenced. With

this instruction it is possible to control the time to the next increment of the counter. See

Table 8.

Table 5.

Write instructions

The writing protocol is illustrated in Figure 10.

First byte

Second byte

Further bytes Action

Instruction Instruction code Instruction Instruction code Parameters

wrt_cmd

1010 0000

device slave write address: slave address

plus write bit

dvs_cmd

0001 0001

stop and reset dividers

0001 0000

start dividers

pwd_cmd

0010 0001

shut down the device

0010 0000

enable the device

32k_cmd

0011 0001

enable output of 32.768 kHz on pin INT

0011 0000

disable output of 32.768 kHz on pin INT

fst_cmd

0100 0001

fast mode; increments counter every

second

0100 0000

fast mode disable

set_cmd

1000 0000

set the counter value

P1[23:16]

parameter with counter values

P2[15:8]

P3[7:0]

Table 6.

Read instructions

The reading protocol is illustrated in Figure 11.

First byte

Further bytes Action

Instruction Instruction code Parameters

rd_cmd[1]

1010 0001

device slave read address: slave address plus

read bit

P1[23:16]

parameter with counter values;

continues to read until no ACK is received;

counter is not updated during this time

P2[15:8]

P3[7:0]

P4[23:16]

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