User's Manual

MC46 Hardware Interface Description
DRAFT
MC46_HD_V02.8xb Page 43 of 98 21.08.2003
3.6.3 CYCLIC SLEEP mode (AT+CFUN=5, 6, 7 and 8)
The functionality levels AT+CFUN=5, AT+CFUN=6, AT+CFUN=7 and AT+CFUN=8 are
referred to as CYCLIC SLEEP modes. The major benefit over the NON-CYCLIC SLEEP
mode is that the serial interface is not permanently blocked and that packet switched calls
may go on without terminating the selected CYCLIC SLEEP mode. This allows MC46 to
become active, for example to perform a GPRS data transfer, and to resume power saving
after the GPRS data transfer is completed.
The four CYCLIC SLEEP modes give you greater flexibility regarding the wake-up
procedures: For example, in all CYCLIC SLEEP modes, you can enter AT+CFUN=1 to
permanently wake up the module. The best choice is using CFUN=7 or 8, since in these
modes MC46 automatically resumes power saving, after you have sent or received a short
message or made a call. CFUN=5 and 6 do not offer this feature, and therefore, are only
supported for compatibility with earlier releases. Please refer to Table 11 for a summary of
all modes.
The CYCLIC SLEEP mode is a dynamic process which alternatingly enables and disables
the serial interface. By setting/resetting the /CTS signal, the module indicates to the
application whether or not the UART is active. The timing of the /CTS signal is described
below.
Both the application and the module must be configured to use hardware flow control
(RTS/CTS handshake). The default setting of MC46 is AT\Q0 (no flow control) which must
be altered to AT\Q3. See [1] for details.
Note: If both serial interfaces ASC0 and ASC1 are connected, both are synchronized. This
means that SLEEP mode takes effect on both, no matter on which interface the AT
command was issued. Although not explicitly stated, all explanations given in this
chapter refer equally to ASC0 and ASC1, and accordingly to /CTS0 and /CTS1.
3.6.4 Timing of the /CTS signal in CYCLIC SLEEP modes
The /CTS signal is enabled in synchrony with the module’s paging cycle. It goes active low
each time when the module starts listening to a paging message block from the base station.
The timing of the paging cycle varies with the base station. The duration of a paging interval
can be calculated from the following formula:
4.615 ms (TDMA frame duration) * 51 (number of frames) * DRX value.
DRX (Discontinuous Reception) is a value from 2 to 9, resulting in paging intervals from 0.47
to 2.12 seconds. The DRX value of the base station is assigned by the network operator.
Each listening period causes the /CTS signal to go active low: If DRX is 2, the /CTS signal is
activated every 0.47 seconds, if DRX is 3, the /CTS signal is activated every 0.71 seconds
and if DRX is 9, the /CTS signal is activated every 2.1 seconds.
The /CTS signal is active low for 4.6 ms. This is followed by another 4.6 ms UART activity. If
the start bit of a received character is detected within these 9.2 ms, /CTS will be activated
and the proper reception of the character will be guaranteed.
/CTS will also be activated if any character is to be sent from the module to the application.