Torwards
AT8563
Symbol
Description
0EH
b1
Timer source clock frequency selection bits. These bits
determine the source clock for the countdown timer, see
Table 26. When not in use, TD1 and TD0 should be set to
‘11’ (1⁄60 Hz) for power saving.
TD1
b0
TD0
Table 26 Timer source clock frequency selection
Timer source clock
TD[1:0]
frequency（Hz）
00
01
10
11
4096
64
1
1/60
Table 27 Timer countdown value register bits description
Description
0FH
Symbol
<timer countdown value>
b7～b0
countdown value n, the counter’s period is “”n/fCLK”
2.8 EXT_CLK test mode
A test mode is available which allows for on-board testing. In this mode it is possible to set
up test conditions and control the operation of the RTC.
The test mode is entered by setting bit TEST1 in the Control/Status1 register. The
CLKOUT pin then becomes an input. The test mode replaces the internal 64 Hz signal with the
signal that is applied to the CLKOUT pin. Every 64 positive edges applied to CLKOUT will then
generate an increment of one second.
The signal applied to the CLKOUT pin should have a minimum pulse width of 300 ns and
a minimum period of 1000 ns. The internal 64 Hz clock, now sourced from CLKOUT, is divided
down to 1 Hz by a 26 divide chain called a pre-scaler. The pre-scaler can be set into a known
state by using the STOP bit. When the STOP bit is set, the pre-scaler is reset to 0. STOP must
be cleared before the pre-scaler can operate again. From a STOP condition, the first 1 s
increment will take place after 32 positive edges on CLKOUT. Thereafter, every 64 positive
edges will cause a 1 s increment.
Remark: Entry into EXT_CLK test mode is not synchronized to the internal 64 Hz clock.
When entering the test mode, no assumption as to the state of the pre-scaler can be made.
You can operate in the following steps:
1. Enter the EXT_CLK test mode; set bit 7 of Control/Status 1 register (TEST = 1)
2. Set bit 5 of Control/Status 1 register (STOP = 1)
3. Clear bit 5 of Control/Status 1 register (STOP = 0)
4. Set time registers (Seconds, Minutes, Hours, Days, Weekdays, Months/Century and
Years) to desired value
•
11
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