SM59D03G2 Datasheet, PDF (37/67 Pages) SyncMOS Technologies,Inc – 8-Bits Micro-controller

SM59D03G2
8-Bits Micro-controller
8KB+ ISP Flash & 1KB RAM embedded
When the master processor wants to transmit a block of data to one of several slaves, it first sends
out an address byte which identifies the target slave. An address byte differs from a data byte in
that the 9^th bit is 1 in an address byte and 0 in a data byte. With SM2 = 1, no slave will be
interrupted by a data byte. An address byte, however, will interrupt all slaves, so that each slave
can examine the received byte and see if it is being addressed. The addressed slave will clear its
SM2 bit and prepare to receive the data bytes that will be coming. The slave that weren’t being
addressed leave their SM2s set and go on their business, ignoring the coming data bytes.
SM2 has no effect in Mode 0, and in Mode 1 can be used to check the validity of the stop bit. In
Mode 1 reception, if SM2 = 1, the receive interrupt will not be activated unless a valid stop bit is
received.
10.2 Baud rates
The baud rate in Mode 0 is fixed:
Mode 0
Baud Rate = ^{System Frequency}
6
The baud rate in mode 2 depends on the value of bit SMOD in SFR PCON. If SMOD = 0 (which is
the value on reset), the baud rate is 1/32 the system frequency. If SMOD = 1, the baud rate is 1/16
the system frequency.
Mode 2
Baud Rate = ^2SMOD × (System Frequency)
32
10.3 Using Timer 1 to Generate Baud Rates.
When Timer 1 is used as the baud rate generator, the baud rates in Modes 1 and 3 are determined
by the Timer 1 overflow rate and the value of SMOD as follows:
Modes 1 and 3 Baud Rate = ^2SMOD × (Timer 1 overflow rate)
32
The Timer 1 interrupt should be disabled in this application. The timer itself can be configured for
either “timer” or “counter” operation, and in any of its 3 running modes. In the most typical
applications, it is configured for “timer” operation, in the auto-reload mode (high nibble of TMOD =
0010B). In that case, the baud rate is given by the formula
Modes 1 and 3 Baud Rate = ^2SMOD × ^{System Frequency}
32 6 ×[256 − TH1]
One can achieve very low baud rates with Timer 1 by leaving the Timer 1 interrupt enabled, and
configuring the timer to run as a 16-bit timer (high nibble of TMOD = 0001B), and using the Timer 1
interrupt to do a 16-bit software reload
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M030
37
Ver.C SM59D03G2 07/2009