User's Manual

User Manual
SM3000 OEM module
Read/Write command
If the module has data to send and it detects that also the host has data to send it will start a read/write
communication sequence.
The host signals the module it has data to send by pulling the RTS line low. In due time the module lowers
the DR line to mark start of communication.
The module will generate a clock signal on the SCLK line. The clock signal consists of groups of 8 pulses.
Each group represents one byte transmitted and received.
The first byte that is outputted on the MOSI line by the module is the read/write command: 0xb0. For the
second byte the host must then output N: the number of bytes it will send and the module will output M: the
number of bytes it will send. The module will then generate a clock signal for max(M,N) bytes. The host
must put its data on the MISO line. The module must put its data on the MOSI line. After sending M bytes
the module will continue sending (max(M,N) – M) bytes which can be ignored by the host. After sending N
bytes the host will continue sending (max(M,N) – N) bytes which can be ignored by the module. When all
bytes are sent the module raises the DR line again to mark end of communication.
12/27 Ambient Systems B.V.