PCA88021 datasheet(9/34 Pages) NXP

9 / 34 page

PCA8802_1

Product data sheet

Rev. 01 — 19 February 2009

9 of 34

NXP Semiconductors

PCA8802

Smartcard RTC

9.5.1.2

The reading protocol

The reading protocol is shown in Figure 11.

9.5.1.3

Reading and writing limitations

As the counter is frozen during interface accesses, all access must be completed within

32 seconds (see Figure 12). If this rule is not adhered to, then counts will be dropped.

Wrt_cmd is slave address plus write bit.

Fig 10. Writing protocol

001aaj213

wrt_cmd

writing 2 consecutive instructions

writing 2 consecutive instructions with instruction parameters

START condition

STOP condition

acknowledge from slave

instruction

wrt_cmd

instruction

instr. parameter 1

instr. parameter 2

instr. parameter 3

instruction

Rd_cmd is slave address plus read bit.

Fig 11. Reading protocol

001aaj207

rd_cmd

1st parameter

reading multiple data parameters

START condition

STOP condition

acknowledge from slave

acknowledge from master

not acknowledge from master

2nd parameter

A3rd parameter

A4th parameter

Anth parameter

Wrt_cmd is slave address plus write bit.

Rd_cmd is slave address plus read bit.

Fig 12. Access restrictions

001aaj205

wrt_cmd/

rd_cmd

instruction transfer

must be < 32 seconds

START condition

STOP condition

acknowledge from slave

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