at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 187

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

21.12 Slow Clock Mode
21.12.1
Figure 21-32. Read/write Cycles in Slow Clock Mode
6384B–ATARM–15-Dec-08
NBS0, NBS1,
NBS2, NBS3,
A0,A1
Slow Clock Mode Waveforms
A[25:2]
NWE
MCK
NCS
SLOW CLOCK MODE WRITE
The SMC is able to automatically apply a set of “slow clock mode” read/write waveforms when
an internal signal driven by the Power Management Controller is asserted because MCK has
been turned to a very slow clock rate (typically 32kHz clock rate). In this mode, the user-pro-
grammed waveforms are ignored and the slow clock mode waveforms are applied. This mode is
provided so as to avoid reprogramming the User Interface with appropriate waveforms at very
slow clock rate. When activated, the slow mode is active on all chip selects.
Figure 21-32
chip selects.
1
Table 21-6.
Read Parameters
NRD_SETUP
NRD_PULSE
NCS_RD_SETUP
NCS_RD_PULSE
NRD_CYCLE
NWE_CYCLE = 3
1
Table 21-6
illustrates the read and write operations in slow clock mode. They are valid on all
Read and Write Timing Parameters in Slow Clock Mode
1
indicates the value of read and write parameters in slow clock mode.
Duration (cycles)
1
1
0
2
2
AT91SAM9G20 Preliminary
NBS0, NBS1,
NBS2, NBS3,
A0,A1
Write Parameters
NWE_SETUP
NWE_PULSE
NCS_WR_SETUP
NCS_WR_PULSE
NWE_CYCLE
A[25:2]
MCK
NRD
NCS
SLOW CLOCK MODE READ
NRD_CYCLE = 2
1
Duration (cycles)
1
1
1
0
3
3
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