ST7538
Figure 4. Packet Mode Timing
CLR_T
T
DS
RXD
T
CRP
TXD
D03IN1406
T
DH
IDLE
IDLE
IDLE
CLR_T
RXD
Control Register Access
The communication with ST7538 Control Register is always synchronous. The access is achieved using
the same lines of the Mains interface (RxD, TxD and CLR/T) plus REG_DATA Line.
With REG_DATA = 1 and
RxTx
=0, the data present on TxD are loaded into the Control Register MSB first.
The ST7538 sampled the TxD line on CLR/T rising edges. The control Register content is updated at the
end of the register access section (REG_DATA falling edge). If more than 24 bits are transferred to
ST7538 only the latest 24 bits are stored inside the Control Register.
With REG_DATA = 1 and
RxTx
=1, the content of the Control Register is sent on RxD port. The Data on
RxD are stable on CLR/T rising edges MSB First.
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