MC33593

MOTOROLA SEMICONDUCTORS PRODUCTS

13

revision 7.0, 5 February 2002

© Motorola, Inc., 2002.

STATE MACHINES

AFTER POR RESET STATE MACHINE

There are 3 different modes for the receiver.

Sleep mode corresponds to the low power consumption mode:

- if SOE=0, the whole receiver is shutdown,

- if SOE=1, the strobe oscillator remains active.

Configuration mode is used for writing or reading the internal registers. In this mode, the SPI is slave and the

receiver is enabled. The crystal oscillator is running and generates the clock for the SPI. This implies that before

the circuit is in sleep mode, a delay corresponding to the crystal oscillator wake-up time must be inserted

between the falling edge on RESETB and the start of the transmission on the SPI lines. The local oscillator is

running as well. This means that demodulated data can be read on DMDAT but are not sent by the SPI.

In Run mode, the receiver is enabled (crystal and local oscillators are running). It is either waiting for an RF

telegram or receiving one.

Figure 14 details the state machine after Power On Reset (POR). The state machine is synchronized by a

sampling clock at 615kHz (sampling period Ts=1.6µs), derivated from the crystal oscillator. The transition time

between state 1 and states 2 or 6 is less than 3

After POR, the circuit is in state 0 and configuration registers’ content is set to the reset value. This enables to

use ROMEO2 in a standalone configuration without any external control.

As long as a low level is applied on RESETB, the circuit stays in state 1. This configuration mode enables to write

or read the internal registers through the SPI interface.

Figure 14: After POR state machine

State 1

Configuration mode

SPI active and slave

RESETB=1

AND DME=0

State 2, see figure 15

State 6, see figure 16

State 0

Sleep mode

SPI disabled

RESETB=0

RESETB=1

AND DME=1

AND SOE=0

RESETB=1

AND DME=1

AND SOE=1

State 0b

Run mode

Raw data on MOSI

SPI disabled

Power-On Reset

Strobe Counter

≠ SR

AND STROBE=0

Strobe Counter=SR

OR STROBE=1

SPI slave

SPI master

SPI disabled

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