External Output Clock (Fout3, Fout1) - Epson S1C17704 Technical Manual

7 OSCILLATOR (OSC)

7.7 External Output Clock (FOUT3, FOUT1)

A divided OSC3 clock (FOUT3) and the OSC1 clock (FOUT1) can be output to external devices.
OSC3 clock
OSC1 clock
FOUT3 output
FOUT3 is a divided OSC3 clock.
Setting up the output pin
The FOUT3 output pin is shared with the P30 port and it functions as the P30 port pin by default. Write 1
to P30MUX (D0/P3_PMUX register) to switch the P30 pin function for the FOUT3 output.
∗ P30MUX: P30 Port Function Select Bit in the P3 Port Function Select (P3_PMUX) Register (D0/0x52a3)
Selecting the FOUT3 clock frequency
The output clock frequency can be selected from three kinds. Select an OSC3 clock division ratio using
FOUT3D[1:0] (D[3:2]/OSC_FOUT register) to set up the clock frequency.
∗ FOUT3D[1:0]: FOUT3 Clock Division Ratio Select Bits in the FOUT Control (OSC_FOUT) Register
Controlling the clock output
Use FOUT3E (D1/OSC_FOUT register) to control the clock output. When FOUT3E is set to 1, the FOUT3
clock is output from the FOUT3 pin and the output is disabled when FOUT3E is set to 0.
∗ FOUT3E: FOUT3 Output Enable Bit in the FOUT Control (OSC_FOUT) Register (D1/0x5064)
Note: The FOUT3 signal is generated asynchronously with writing to FOUT3E, therefore, a hazard will
occur when the output is enabled or disabled.
7-8
Divider
(1/1–1/4)
Division ratio select
Figure 7.7.1 Clock Output Circuit
(D[3:2]/0x5064)
Table 7.7.1 Selecting Division Ratio for Generating FOUT3 Clock
FOUT3D[1:0]
0x3
0x2
0x1
0x0
FOUT3E
FOUT3 output (P30)
Figure 7.7.2 FOUT3 Output
P30 port
FOUT3
output circuit
On/Off P30 function
control select
P13 port
FOUT1
output circuit
On/Off P13 function
control select
Division ratio
Reserved
OSC3•1/4
OSC3•1/2
OSC3•1/1
(Default: 0x0)
0 1
EPSON
FOUT3(P30)
FOUT1(P13)
0
S1C17704 TECHNICAL MANUAL