Setting Synchronous Clock; Selecting Source Clock; Selecting Synchronous Clock Format - Epson S1C63003 Technical Manual

13 SeRial inTeRFaCe
13.5

Setting Synchronous Clock

13.5.1

Selecting Source Clock

When the serial interface is used in master mode, it uses the internal clock supplied from the clock manager as the
synchronous clock for data transfer. The clock manager generates six serial interface clocks by dividing the OSC1
or OSC3 clock. The synchronous clock used in master mode can be selected from seven types (the above six clocks
and the programmable timer 1 output clock). Use the SIFCKS[2:0] register to select one of them as shown in Table
13.5.1.1.
f
OSC1
f
OSC3
* The maximum clock frequency is limited to 1 MHz.
When programmable timer 1 is selected, the programmable timer 1 underflow signal is divided by 2 before it is used
as the synchronous clock. In this case, the programmable timer must be controlled before operating the serial inter-
face. Refer to the "Programmable Timer" chapter for controlling the programmable timer.
Fix SIFCKS[2:0] at "0" in slave mode.
At initial reset, "Off (slave mode)" is selected.
13.5.2

Selecting Synchronous Clock Format

The format (polarity and phase) of the synchronous clock for the serial interface can be configured using the
SCPS[1:0] register.
At initial reset, the clock polarity is set to positive and the phase is set to the rising edge.
See Figure 13.6.5.1 for the data transfer timings by the synchronous clock format selected.
13-4
Table 13. 5.1.1 Serial interface clock frequencies
SIFCKS[2:0]
7
6
5
4
3
2
1
0
: OSC1 oscillation frequency. ( ) indicates the frequency when f
: OSC3 oscillation frequency
Table 13. 5.2.1 Configuration of synchronous clock format
SCPS[1:0]
3 Negative (SCLK)
2 Negative (SCLK)
1 Positive (SCLK)
0 Positive (SCLK)
Seiko epson Corporation
SIF clock (master mode)
f / 4 *
OSC3
f / 2 *
OSC3
f / 1 *
OSC3
Programmable timer 1 *
f / 4 (8 kHz)
OSC1
f / 2 (16 kHz)
OSC1
f / 1 (32 kHz)
OSC1
Off (slave mode) *
Polarity Phase
Rising edge (↑)
Falling edge (↓)
Falling edge (↓)
Rising edge (↑)
S1C63003/004/008/016 TeChniCal Manual
= 32 kHz.
OSC1
(Rev. 1.1)