34RC02 datasheet(7/16 Pages) CATALYST

7 / 16 page

CAT34RC02

Doc No. 1052, Rev. K

The PSWP flag can be set (forever) by issuing a ‘Byte

Write’ command, with the Slave address preamble set to

‘6h’, followed by a ‘don’t care’ address, followed by ‘don’t

care’ data and a STOP condition. The CAT34RC02 will

acknowledge the Slave address, dummy byte address

and dummy data (Fig. 10). The PSWP flag will be

permanently set (after the internal write cycle is

completed).

The SWP commands are shown in Table 1.

Table 1. SWP Commands

DR/

The CAT34RC02 will not acknowledge RSWP or PSWP

commands, once the PSWP flag is set. If the PSWP flag

is not set, but the WP pin is HIGH, then the CAT34RC02

will react to RSWP or PSWP commands as follows: if the

command attempts to ‘flip’ one of the two SWP switches,

then the CAT34RC02 will respond the same way the

regular memory would, i.e. the command and address

(in this case dummy) are acknowledged, but the data (in

this case dummy) will not be acknowledged; if the

command attempts to ‘reaffirm’ one of the two switches,

then the CAT34RC02 will not acknowledge the command

itself. In addition, the CAT34RC02 will not acknowledge

a ‘reaffirming’ SWP command, even if the WP pin is

LOW.

Power-On Reset (POR)

The CAT34RC02 incorporates Power-On Reset (POR)

circuitry which protects the device against malfunctioning

while VCC is lower than the recommended operating

voltage.

The device will power up into a read-only state and will

power-down into a reset state when VCC crosses the

POR level of ~1.3V.

READ OPERATIONS

Immediate Address Read

In standby mode, the CAT34RC02 internal address

counter points to the data byte immediately following the

last byte accessed by a previous operation. If the

‘previous’ byte was the last byte in memory, then the

address counter will point to the first memory byte, etc.

If the CAT34RC02 decodes a Slave address with a ‘1’ in

the R/

W bit position (Fig. 8), it will issue an ACK in the 9th

clock cycle, and will then transmit the data byte being

pointed at by the address counter. The Master can then

stop further transmission by issuing a NoACK, followed

by a STOP condition.

Selective Read

The READ operation can also be started at an address

different from the one stored in the address counter. The

Figure 8. Immediate Address Read Timing

SCL

SDA

8th Bit

STOP

NO ACK

DATA OUT

SLAVE

ADDRESS

DATA

BUS ACTIVITY:

MASTER

SDA LINE

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