
7 ClOCK GeneRaTOR (ClG)
7-10
Seiko epson Corporation
S1C17624/604/622/602/621 TeChniCal Manual
ReSeT and nMi input noise Filters
7.8
Since accidental activation of RESET or NMI by noise in the external input signals will cause unintended resetting
or NMI processing, the CLG module incorporates noise filters operated by the system clock (SYSCLK). The filters
remove noise from these signals before they reach the S1C17 Core or peripheral modules. Separate noise filters are
used for each signal. You can select to use or bypass them individually.
RESET input noise filter: Filters noise when RSTFE/OSC_NFEN register = 1; bypassed when RSTFE = 0
NMI input noise filter: Filters noise when NMIFE/OSC_NFEN register = 1; bypassed when NMIFE = 0
notes: • The RESET input noise filter should normally be enabled.
• The S1C17624/604/622/602/621 has no external NMI input pin, but the watchdog timer NMI
request signal passes through the filter.
Control Register Details
7.9
9.1 List of CLG Registers
Table 7.
address
Register name
Function
0x4020
PSC_CTL
Prescaler Control Register
Controls prescalers.
0x5060
OSC_SRC
Clock Source Select Register
Selects the clock source.
0x5061
OSC_CTL
Oscillation Control Register
Controls oscillation.
0x5062
OSC_NFEN
Noise Filter Enable Register
Enables/disables noise filters.
0x5064
OSC_FOUT
FOUT Control Register
Controls FOUTH/FOUT1 clock outputs.
0x5080
CLG_PCLK
PCLK Control Register
Controls the PCLK supply.
0x5081
CLG_CCLK
CCLK Control Register
Configures the CCLK division ratio.
The CLG module registers are described in detail below. These are 8-bit registers.
note: When data is written to the registers, the “Reserved” bits must always be written as 0 and not 1.
Prescaler Control Register (PSC_CTl)
Register name address
Bit
name
Function
Setting
init. R/W
Remarks
Prescaler
Control Register
(PSC_CTl)
0x4020
(8 bits)
D7–2 –
reserved
–
–
–
0 when being read.
D1
PRunD
Run/stop select in debug mode
1 Run
0 Stop
0
R/W
D0
PRun
Prescaler run/stop control
1 Run
0 Stop
0
R/W
D[7:2]
Reserved
D1
PRunD: Run/Stop Select Bit in Debug Mode
Selects the operating status of the peripheral circuits that operate with PCLK in debug mode.
1 (R/W): Run
0 (R/W): Stop (default)
Setting PRUND to 1 enables the peripheral circuits that operate with PCLK to run even in debug mode.
Setting it to 0 will stop them when the S1C17 Core enters debug mode. Set PRUND to 1 to maintain
running status for these peripheral circuits in debug mode.
D0
PRun: Prescaler Run/Stop Control Bit
Starts or stops prescaler operation.
1 (R/W): Start operation
0 (R/W): Stop (default)
Write 1 to PRUN to operate the prescalers for peripheral modules. Write 0 to PRUN to stop the prescalers.
Clock Source Select Register (OSC_SRC)
Register name address
Bit
name
Function
Setting
init. R/W
Remarks
Clock Source
Select Register
(OSC_SRC)
0x5060
(8 bits)
D7–2 –
reserved
–
–
–
0 when being read.
D1
hSClKSel High-speed clock select
1 OSC3
0 IOSC
0
R/W
D0
ClKSRC
System clock source select
1 OSC1
0 HSCLK
0
R/W
D[7:2]
Reserved