EM A3024 Very low power 8-bit 32 khz rtc with digital trimming, user ram and high level integration Datasheet

R
EM MICROELECTRONIC-MARIN SA
A3024
Very Low Power 8-Bit 32 kHz RTC with
Digital Trimming, User RAM and High Level Integration
Features
Typical Operating Configuration
WR or R/W
RD or DS
IRQ
n Digital trimming and temperature compensation
facilities
n Can be synchronized to 50 Hz or nearest s/min
n 50 ns access time with 50 pF load capacitance
n Standby on power down typically 1.2 mA
n Universal interface compatible with both Intel and Motorola
n Simple 8 bit interface with no delays or busy flags
n 16 bytes of user RAM
n Power fail input disables during power up / down or reset
n Bus can be tri-state in power fail mode
n Wide voltage range, 2.0 V to 5.5 V
n 12 or 24 hour data formats
n Time to 1/100 of a second
n Leap year correction and week number calculation
n Alarm and timer interrupts
n Programmable interrupts: 10 ms, 100 ms, s or min
n Sleep mode capability
n Alarm programmable up to one month
n Timer measures elapsed time up to 24 hours
n Temperature range -40 to +85 OC
n Packages DIP20 and SO20
CPU
CS
IRQ
RD
X in
WR A3024
A/D
X out
AD0 to AD7
Address Bus
Data Bus
Address
Decoder
Description
CS
RD
WR
The A3024 is a low power CMOS real time clock. Standby
current is typically 1.2 mA and the access time is 50 ns. The
interface is 8 bits with multiplexed address and data bus.
Multiplexing of address and data is handled by the input line
A/D. There are no busy flags in the A3024, internal time update
cycles are invisible to the user’s software. Time data can be
read from the A3024 in 12 or 24 hour data formats. An external
signal puts the A3024 in standby mode. Even in standby, the
A3024 pulls the IRQ pin active low on an internal alarm interrupt.
Calendar functions include leap year correction and week
number calculation. Time precision can be achieved by digital
triming. The A3024 can be synchronized to an external 50 Hz
signal or to the nearest second or minute.
Fig. 1
Pin Assignment
DIP20 / SO20
SYNC
PF
AD0
AD1
AD2
AD3
A/D
IRQ
VSS
XIN
Applications
n
n
n
n
n
RAM
Industrial controllers
Alarm systems with periodic wake up
PABX and telephone systems
Point of sale terminals
Automotive electronics
A3024
NC
AD7
AD6
AD5
AD4
RD
WR
CS
VDD
XOUT
Fig. 2
1
R
A3024
Absolute Maximum Ratings
Parameter
Symbol Conditions
Maximum voltage at VDD
VDDmax
Vmax
Vmin
TSTOmax
TSTOmin
Max. voltage at remaining pins
Min. voltage on all pins
Maximum storage temperature
Minimum storage temperature
Maximum electrostatic discharge
to MIL-STD-883C method 3015
Maximum soldering conditions
VSmax
TSmax
or electric fields; however, it is advised that normal precautions
must be taken as for any other CMOS component. Unless
otherwise specified, proper operation can only occur when all
terminal voltages are kept within the supply voltage range.
Unused inputs must always be tied to a defined logic voltage
level.
VSS + 7.0V
VDD + 0.3V
VSS - 0.3V
+125OC
-55OC
Operating Conditions
Parameter
1000V
Symbol Min. Typ. Max. Units
Operating temperature
Logic supply voltage
Supply voltage dv/dt
(power-up & down)
Decoupling capacitor
Crystal Characteristics
Frequency
Load Capacitance
Series resistance
250OC x 10s
Table 1
Stresses above these listed maximum ratings may cause
permanent damage to the device. Exposure beyond specified
operating conditions may affect device reliability or cause
malfunction.
Handling Procedures
TA
VDD
-40
2.0
100
7
C
V
V/ms
nF
6
dv/dt
f
CL
RS
O
+85
5.0 5.5
32.768
8.2 12.5
35
50
kHz
pF
kW
This device has built-in protection against high static voltages
Table 2
Electrical Characteristics
VDD = 5.0V ± 10%, VSS = 0 V, TA = -40 to +85OC, unless otherwise specified
Parameter
Symbol Test Conditions
1)
Standby current
2)
IDD
IRQ (open drain)
Output low voltage
Output low voltage
VOL
VOL
IOL = 8 mA
IOH = 1 mA, VDD = 2 V
VIL
VIH
VOL
VOH
VPFL
VH
ILS
IIN
ITS
TA = +250C
TA = +250C
IOL = 6 mA
IOH = 6 mA
VSTA
VSTA
TSTA
TA ³ +25OC
Df/f
fsta
tsta
TA = +25 C addr. 10 hex = 00 hex
3)
2.0 £ VDD £ 5.5 V
addr. 10 hex = 00 hex
Start-up time
Frequency Characteristics
Frequency tolerance
Frequency stability
Temperature stability
2)
3)
4)
VDD = 3 V, PF = 0
VDD = 5 V, PF = 0
CS = 4 MHz, RD = VSS,
WR = VDD
Dynamic current
Inputs and Outputs
Input logic low
Input logic high
Output logic low
Output logic high
PF activation voltage
PF hysteresis
Pullup on SYNC
Input leakage
Output tri-state leakage
Oscillator Characteristics
Starting voltage
1)
IDD
Min.
Typ.
Max.
Units
1.2
2
10
15
1.5
mA
mA
mA
0.4
0.4
V
V
0.2 × VDD
V
V
V
V
V
mV
mA
nA
nA
0.8 × VDD
0.4
2.4
0.5 × VDD
100
0
TA = +25 C
VILS = 0.8 V
VSS<VIN<VDD
CS = 1
20
10
10
1000
1000
V
V
s
2
2.5
1
O
4)
210
1
see Fig. 5
251
5
With PFO = 0 (VSS) all I/O pads can be tri-state, tested.
With PFO = 1 (VDD), CS = 1 (VDD) and all other I/O pads fixed to VDD or to VSS: same standby current, not tested.
All other inputs to VDD and all outputs open.
At a given temperature.
See Fig. 4
2
ppm
ppm/V
ppm
Table 3
R
A3024
Typical Standby Current at VDD = 5 V
IDD [mA]
Typical standby current range at VDD = 5 V
5
4
3
2
1
0
-50
25
50
80
95
0
TA [ C]
Fig. 3
Typical Frequency on IRQ
DF ppm
F0
Address 10 hex = 00 hex
250
Quartz recommended
32.768 Hz ± 30 ppm
with 8.2 pF load capacitance
200
150
100
50
0
-50
-30
-10
10
30
50
70
90
TA [0C]
Fig. 4
Characteristic of a Quartz
DF
F0
[ppm]
DF
ppm
2
= - 0.038 O 2 (T - TO) ±10%
FO
C
.
x.
DF/FO = the ratio of the change in frequency to the nominal value
expressed in ppm (It can be thought of as the frequency
deviation at any temperature.)
O
= the temperature of interest in C
T
O
TO
= the turnover temperature (25 ±5 C)
min
-200
ma
Frequency ratio [ppm]
-100
-300
To determine the clock error (accuracy) at a given temperature, add
O
the frequency tolerance at 25 C to the value obtained from the
formula above.
-400
TO-100
TO - 50
TO
TO+50
O
Temperature [ C]
TO+100
T [OC]
Fig. 5
3
R
A3024
Timing Characteristics
0
VDD = 5.0 ± 10%, VSS = 0 V, and TA = -40 to +85 C
1)
Parameter
Symbol
Chip select duration, write cycle
Write pulse duration
Time between two transfers
1)
RAM access time
2)
Data valid to Hi-impedance
3)
Write data settle time
4)
Data hold time
Advance write time
PF response delay
Rise time (all timing waveform signals)
Fall time (all timing waveform signals)
5)
CS delay after A/D
CS delay to A/D
tCS
tWR
tW
tACC
tDF
tDW
tDH
tADW
tPF
tR
tF
tA/Ds
tA/Dt
Test Conditions
Min.
Typ.
Max.
Units
60
ns
ns
ns
ns
40
ns
50
50
100
CLOAD = 50 pF
10
50
30
50
10
10
100
200
200
5
10
ns
ns
ns
ns
ns
ns
ns
ns
Table 4
tACC starts from RD (DS) or CS, whichever activates last
Typically, tACC = 5 + 0.9 CEXT in ns; where CEXT (external parasitic capacitance) is in pF
2)
tDF starts from RD (DS) or CS, whichever deactivates first
3)
tDW ends at WR (R/W) or CS, whichever deactivates first
4)
tDH starts from WR (R/W) or CS, whichever deactivates first
5)
A/D must come before a CS and RD or a CS and WR combination. The user has to guarantee this.
Timing Waveforms
Read Timing for Intel (RD and WR pulse) and Motorola (DS or RD pin tied to CS, and R/W)
tCS
tF
CS
tW
tR
tA/Ds
A/D
tA/Dt
RD/DS
tACC
tDF
DATA
DATA VALID
Fig. 6a
4
R
A3024
Intel Interface
Write Timing
tCS
tW
CS
tA/Ds
tA/Dt
A/D
RD
tWR
WR
tDH
tDW
DATA
DATA VALID
Fig. 6b
Write
CS
RD
WR
A/D
Valid Address
Data Bus
D0 to D7
Valid Data
Fig. 6c
Read
CS
RD
WR
A/D
Data Bus
D0 to D7
Valid Address
Valid Data
Fig. 6d
5
R
A3024
Motorola Interface
Motorola Write
tCS
tW
CS
tA/Ds
tA/Dt
A/D
DS
tADW
R/W
tDH
tDW
DATA
DATA VALID
Fig. 6e
Write
CS
DS
R/W
A/D
Valid Address
Data Bus
D0 to D7
Valid Data
Fig. 6f
Read
CS
DS
R/W
A/D
Data Bus
D0 to D7
Valid Address
Valid Data
Fig. 6g
6
R
A3024
General Block Diagram
Xin
Oscillator and
Divider Chain
Xout
100 Hz
8
Trim Bus
Trimming and Alarm
Logic
Reserved clock
and timer area
Clock
and
Timer
00
01
02
10
20
28
30
Hex Address
34
40
A/D
CS
WR
RD
SYNC
clock
RAM
(data space)
alarm
timer
Control Block and
Output Buffers
Address / Data
status 0
status 1
status 2
digital trimming
43
50
16 bytes of user RAM
5F
F0 clock and timer command
F1 clock command
F2 timer command
RAM
(address command space)
Address / Data
IRQ + PF
Logic
Control Bus
IRQ
Power Fail
Digital Trimming
IRQ
32768 Hz
:42/43
Oscillator
:32
1kHz
:10
100 Hz
Timer
1/100 Sec. Min. Hour
INIB.
Reg.
:31
INIB.RAM
Reset INIT
Reset WR F0 F1
INIT. Bit
Timer RAM
Reset Logic
Write F0, F1, F2
8
Alarm RAM
COMP
Reset WR F2
Clock RAM
Reset WR F1
:10
100 Hz
Clock
1/100 Sec. Min. Hour Day Month Year W/D W #
1 Hz
Fig. 7
7
R
A3024
Pin Description
initialisation bit (addr. 2 bit 4) and then a 0. This sets the
Frequency Tuning bit and clears all other status bits.
DIP20 and SO20 Packages
Pin Name
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
SYNC
PF
AD0
AD1
AD2
AD3
A/D
IRQ
VSS
XIN
XOUT
VDD
CS
WR
RD
AD4
AD5
AD6
AD7
NC
The time and date parameters should then be loaded into the
RAM (addr. 20 to 28 hex) and then transferred to the reserved
clock area using the clock command followed by a write.
Description
Time synchronization
Power fail
Bit 0 from MUX address / data bus
Bit 1 from MUX address / data bus
Bit 2 from MUX address / data bus
Bit 3 from MUX address / data bus
Address / data decode
Interrupt request
Supply ground (substrate)
Oscillator input
Oscillator output
Positive supply terminal
Chip select
WR (Intel) or R/W (Motorola)
RD (Intel) or DS (Motorola)
Bit 4 from MUX address / data bus
Bit 5 from MUX address / data bus
Bit 6 from MUX address / data bus
Bit 7 from MUX address / data bus
No connection
I
I
I/O
I/O
I/O
I/O
I
O
GND
I
O
PWR
I
I
I
I/O
I/O
I/O
I/O
-
The digital trimming register must then be initialised by
writing 210 (D2 hex) to it, if Frequency Tuning is not
required. After having written a value to the digital
trimming register the frequency tuning mode bit can be
cleared.
RAM Configuration
The RAM area of the A 3024 has a reserved clock and time area,
a data space, user RAM and an address command space (see
Table 9 or Fig. 7). The reserved clock and timer area is not
directly accessible to the user, it is used for internal time
keeping and contains the current time and date plus the timer
parameters.
Data Space
All locations in the data space are Read/Write. The data space
is directly accessible to the user and is divided into five areas :
Status Registers - three registers used for status and control
data for the device (see Tables 6, 7 and 8).
Digital Trimming Register - a special function described
under “Frequency Tuning”.
Table 5
Time and Date Registers - 9 time and date locations which are
loaded with, either the current time and date parameters from
the reserved clock area or the time and date parameters to be
transferred to the reserved clock area.
Functional Description
Power Supply, Data Retention and Standby
The A3024 is put in standby mode by activating the PF input.
When pulled logic low, PF will disable the input lines, and
immediately take to high impedance the lines AD 0-7. Input
states must be under control whenever PF is deactivated. If no
specific power fail signal can be provided, PF can be tied to the
system RESET. Even in standby the interrupt request pin IRQ
will pull to ground upon an unmasked alarm interrupt
occurring.
Alarm Registers - 5 locations used for setting the alarm
parameters.
Timer Registers - 4 locations which are loaded with either the
timer parameters from the reserved timer area or the timer
parameters to be transferred to the reserved time area.
User RAM
The A3024 has 16 bytes of general purpose RAM available for
the users applications. This RAM block is located at addresses
50 to 5F hex and is maintained even in the standby mode (PF
active). The commands, or the time set lock bit, have no effect
on the user RAM block. Reading or writing to the user RAM is
similar to reading or writing to any system RAM address.
Initialisation
When power is first applied to the A3024 all registers have a
random value.
To initialise the A3024, software must first write a 1 to the
8
R
A3024
Address Command Space
Status Words
This space contains the three commands used for carrying out
the transfers between the Time and Date Register and / or the
Timer Registers and the reserved clock and timer area.
Status 0 - Address 00 Hex
7 6 5 4 3 2 1 0
Read / Write bits
0 - disabled / 24 hour
1 - enabled / 12 hour
RAM Map
Address
Dec Hex
frequency tuning mode
pulse enable / disable
alarm enable / disable
timer enable / disable
24 hour / 12 hour 1)
time set lock
test bit 0
test bit 1
Data Space
Status
00
00
status 0
01
01
status 1
02
02
status 2
Special purpose
16
10
digital trimming
Clock
32
20
1/100 second
33
21
seconds
34
22
minutes
1)
35
23
hours
36
24
date
37
25
month
38
26
year
39
27
week day
40
28
week number
Alarm
1/100 second
48
30
49
31
seconds
50
32
minutes
1) 2)
51
33
hours
date
52
34
Timer
64
40
1/100 second
65
41
seconds
66
42
minutes
67
43
hours
User RAM
50
user RAM, byte 0
80
51
user RAM, byte 1
81
52
user RAM, byte 2
82
53
user RAM, byte 3
83
54
user RAM, byte 4
84
55
user RAM, byte 5
85
56
user RAM, byte 6
86
57
user RAM, byte 7
87
58
user RAM, byte 8
88
59
user RAM, byte 9
89
5A user RAM, byte 10
90
5B user RAM, byte 11
91
5C user RAM, byte 12
92
5D user RAM, byte 13
93
5E user RAM, byte 14
94
5F
user RAM, byte 15
95
Address Comand Space
240 F0
clock and timer transfer
241 F1
clock transfer
242 F2
timer transfer
Table 6
Status 1 - Address 01 Hex
7 6 5 4 3 2 1 0
Read / Write bits
0 - masked / no event
1 - unmasked / event
pulse mask
alarm mask
timer mask
reserved
pulse flag
alarm flag
timer flag
reserved
Table 7
Status 2 - Address 02 Hex
7 6 5 4 3 2 1 0
Read / Write bits
Parameter
0 - disabled
1 - enabled
pulse every 10 ms
pulse every 100 ms
pulse every second
pulse every minute
initialisation bit
SYNC 50 Hz
SYNC second
SYNC minute
Table 8
1)
The MSB (bit 7) of the hours byte (addr. 23 hex for the clock
and 33 hex for the alarm) are used as AM/PM indicators in the
12 hour time data format and reading of the hours byte
must be preceded by masking of the AM/PM bit. A set AM/PM
bit indicates PM. In the 24 hour time data format the bit will
always be zero.
2)
The alarm hours, addr. 33 hex, must always be rewritten after a
change between 12 and 24 hour modes.
Range
0-255
00-99
00-59
00-59
00-23
01-31
01-12
00-99
01-07
00-53
00-99
00-59
00-59
00-23
01-31
00-99
00-59
00-59
00-23
Table 9
9
R
A3024
reserved clock and timer area.
The commands take place in two steps as do all other
communications. The command address is sent with A/D low.
This is followed by either a read (RD) or a write (WR), with A/D
high, to determine the direction of the transfer. If the second
step is a read then the data is transferred from the reserved
clock and timer area to the RAM and if the second step is a write
then the data that has already been loaded into the RAM clock
and/or timer locations is transferred to the reserved clock
and/or timer area.
Communication
Data transfer is in 8 bit parallel form. All time data is in packed
BCD format with tens data on lines AD 7 - 4 and units on lines
AD 3 - 0. To access information within the RAM (see Fig. 7) first
write the RAM address, then read or write from or to this
location. Fig 8 shows the two steps needed.
The lines AD 0 - 7 will be treated as an address when pin A/D is
low, and as data when A/D is high. Pin A/D must not change
state during any single read or write access. One line of the
address bus (e.g. A0) can be used to implement the A/D signal
(see "Typical Operating Configuration", Fig. 1). Until a new
address is written, data accesses (A/D high) will always be to
the same RAM address.
Clock and Calendar
The time and date locations in RAM (see Table 9) provide
access to the 1/100 seconds, seconds, minutes, hours, date,
month, year, week day, and week number. These parameters
have the ranges indicated in Table 9. The A3024 may be
programmed for 12 or 24 hour time format (see section "12/24
Data Format"). If a parameter is found to be out of range, it will
be cleared when the units value on its being next incremented is
equal to or greater than 9 eg. B2 will be set to 00 after the units
have incremented to 9 (ie. B9 to 00). The device incorporates
leap year correction and week number calculation at the
beginning of a year. If the first day of the year is day 05, 06 or 07
of the week, then it is given a zero week number, otherwise it
becomes week one. Week days are numbered from 1 to 7 with
Monday as day 1.
Reading of the current time and date must be preceded by a
clock command. The time and date from the last clock
command is held unchanged in RAM.
When transferring data to the reserved clock and timer area
remember to clear the time set lock bit first.
Communication Sequence
A/D = 0
Write RAM address
to the A3024
A/D = 1
Read or write data from or to
the above address
Fig. 8
Access Considerations
The communication sequence shown in Fig. 8 is re-entrant.
When the address is written to the A3024 (ie. first step of the
communication sequence) it is stored in an internal address
latch. Software can read the internal address latch at any time
by holding the A/D line low during a read from the A3024. So, for
example, an interrupt routine can read the address latch and
push it onto a stack, popping it when finished to restore the
A3024.
Timer
The timer can be used either for counting elapsed time, or for
giving an interrupt (IRQ) on being incremented from
23:59:59:99 to 00:00:00:00. The timer counts up with a
resolution of 1/100 second in the timer reserved areas. The
timer enable / disable bit (addr. 00 hex, bit 3) must be set by
software to allow the timer to be incremented. The timer is
incremented in the reserved timer area, every internal time
update (10 ms). The timer flag (addr. 01 hex, bit 6) is set when
the timer rolls over from 23:59:59:99 to 00:00:00:00 and the IRQ
becomes active if the timer mask bit (addr. 01, bit 2) is set. The
IRQ will remain active until software acknowledges the interrupt
by clearing the timer flag. The timer is incremented in the
standby mode, however it will not cause IRQ to become active
until power (VDD) has been restored.
Note: The user should ensure that a time lapse of at least 60
microseconds exists between the falling edge of the IRQ and
the clearing of the timer flag.
NB. Alarm and timer interrupt routines can reprogram the alarm
and timer without it being necessary to read or reprogram the
clock.
Commands
The commands allow software to transfer the clock and timer
parameters in a sequence (eg. seconds, minutes, hours, etc.)
without any danger of an internal time update with carry over
corrupting the data. They also avoid delaying internal time
updates while using the A3024, as updates occuring in the
reserved clock and timer area are invisible to software. Software
writes or reads parameters to or from the RAM only.
There are three commands that occupy the command address
space in the RAM. The function of these commands is to
transfer data from the reserved clock and timer area to the RAM
or to transfer data in the opposite direction, from the RAM to the
10
R
A3024
Reading the Clock
[Pin 7 = A/D]
Setting the Timer ( Time Set Lock Bit = 0)
[Pin 7 = A/D]
Start
Start
A/D = 0
Write 1/100 sec. address (40 hex)
to the A3024
A/D = 1
Write 1/100 sec. data to the RAM
A/D = 0
Write sec. address (41 hex) to the
A3024
A/D = 1
Write sec. data to the RAM
A/D = 0
Write min. address (42 hex) to
the A3024
Read 1/100 sec. data from the
RAM
A/D = 1
Write min. data to the RAM
A/D = 0
Write sec. address (21 hex) to the
A3024
A/D = 0
Write hours address (43 hex) to
the A3024
A/D = 1
Read sec. data from the RAM
A/D = 1
Write hours data to the RAM
A/D = 0
Write min. address (22 hex) to
the A3024
A/D = 0
Write timer command (addr. F2 hex)
to the A3024
A/D = 1
Read min. data from the RAM
A/D = 1
Write F2 hex to the A3024 to
copy the timer parameters from
RAM to the reversed timer area
A/D = 0
Write clock command
(addr. F1 hex) to the A3024
A/D = 1
Read data from the A3024 to
copy the timer parameters from
the reversed clock area to the RAM.
A data read has no significance
A/D = 0
Write 1/100 sec. address (20 hex)
to the A3024
A/D = 1
End
End
Fig. 10
Fig. 9
Note : Commands are only valid as commands when the A/D
line is low. Writing F2 hex with the A/D line high, as in the last box
of Fig. 8, serves only to activate the A3024 write pin which
determines the direction of transfer.
11
R
A3024
Alarm
bits 5 to 7 at addr. 02 hex, in accordance with Table 8. If more
than one bit is set then all the synchronization bits are disabled.
If the SYNC input is set low for longer than 200 ms, while in the
synchronization mode, the clock will synchronize to the falling
edge of the signal. Synchronization to the nearest second
implies that the 1/100 seconds are cleared to zero and if the
contents were > 50, the seconds register is incremented.
Synchronization to the nearest minute implies that the seconds
are cleared to zero and if the contents were > 30, the minutes
register is incremented. Fractions of seconds are cleared.
An alarm date and time may be preset in RAM addresses 30 to
34 hex. The alarm function can be activated by setting the alarm
enable / disable bit (addr. 00 hex, bit 2). Once enabled the
preset alarm time and date are compared, every internal time
update cycle (10 ms), with the clock parameters in the reserved
clock area. When the clock parameters equal the alarm
parameters the alarm flag (addr. 01 hex, bit 5) is set. If the alarm
mask bit (addr. 01 hex, bit 1) is set, the IRQ pin goes active. The
alarm flag indicates to software the source of the interrupt. IRQ
will remain active until software acknowledges the interrupt by
clearing the alarm flag. If the alarm is enabled, and an alarm
address set to FF hex, this parameter is not compared with the
associated clock parameter. Thus it is possible to achieve a
repeat feature where an alarm occurs every programmed
number of seconds, or seconds and minutes, or seconds,
minutes and hours. The A3024 pulls the open drain IRQ line
active low during standby when an alarm interrupt occurs.
If the 12/24 hour mode is changed then the alarm hours
must be re-initialised.
Note: The user should ensure that a time lapse of at least 60
microseconds exists between the falling edge of the IRQ and
the clearing of the alarm flag.
Pulse
There are 4 programmable pulse frequencies available on the
A3024, these are every 10 ms, 100 ms, second or minute. The
pulse feature is activated by setting the pulse enable / disable
bit at address 00, bit 1. The pulse frequency is selected by
setting one of the bits 0 to 3 at address 02 hex (see Table 8). If
more than one of the pulse bits are set then the feature is
disabled. At the selected interval the pulse flag bit (addr. 01 hex,
bit 4) is set. If the pulse mask bit (addr. 01 hex, bit 0) is set then
the IRQ pin goes active. The pulse flag indicates to software the
source of the interrupt. IRQ will remain active until software
acknowledges the interrupt by clearing the pulse flag. The
pulse feature is disabled while in standby. Upon power
restoration the pulse feature is enabled if enabled prior to
standby. See also the section "Frequency Tuning".
IRQ
The IRQ output is used by 4 of the A3024's features.
These are:
1) Pulse, to provide periodic interrupts to the microprocessor
at preprogrammed intervals;
Note: The user should ensure that a time lapse of at least 60
microseconds exists between the falling edge of the IRQ and
the clearing of the pulse flag.
2) Alarm to provide an interrupt to the microprocessor at a
preprogrammed time and date;
Time Set Lock
3) Timer, to provide an interrupt to the microprocessor when
the timer rolls over from 23:59:59:99 to 00:00:00:00; and
The time set lock control bit is located at address 00 hex, bit 5
(see Table 6). When set by software, this bit disables any
transfer from the RAM to the reserved clock and timer area as
well as inhibiting any write to the digital trimming register at
address 10 hex. When the time set lock bit is set the following
transfer operations are disabled:
4) Frequency trimming (see section "Frequency Trimming").
The first 3 features listed are similar in the way they provide
interrupts to the microprocessor. Each of the 3 has an enable /
disable bit, a flag bit, and an interrupt mask bit. The enable /
disable bit allows software to select a feature or not. A set flag bit
indicates that an enable feature has reached its interrupt
condition. Software must clear the flag bit. The interrupt mask
bit allows or disallows the IRQ output to become active when
the flag bit is set. The IRQ output becomes active whenever any
interrupt flag is set which also has its mask bit set. For all
sources of maskable interrupts within the A3024, the IRQ output
will remain active until software clears the interrupt flag. The IRQ
output is the logical OR of all the unmasked interrupt flags. The
IRQ output is open drain so an external pullup to VDD is needed.
In standby (PF active) the IRQ output will be active if the alarm
mask bit (addr. 01 hex, bit 1) is set and the alarm flag is also set.
The timer or the pulse feature cannot cause the IRQ output to
become active while in standby.
The clock command followed by write,
the timer command followed by write,
the clock and timer command followed by write, and
writing to the digital trimming register.
A set bit prevents unauthorized overwriting of the reserved
clock and timer area. Reading of the reserved clock and timer
area, using the commands, is not affected by the time set lock
bit. Clearing the time set lock bit by software will re-enable the
above listed commands. On initialisation the time set lock bit is
cleared. The time set lock bit does not affect the user RAM (addr.
50 to 5F hex).
Frequency Tuning
The A3024 offers a key feature called "Digital Trimming", which
is used for the clock accuracy adjustment. Unlike the traditional
capacitor trimming method, which tunes the crystal oscillator,
the digital trimming acts on the divider chain, allowing the clock
adjustment by software. The oscillator frequency itself is not
affected.
Synchronization
There are 3 ways to synchronize the A3024. It can be
synchronized to 50 Hz, the nearest second, or the nearest
minute. Synchronization mode is selected by setting one of the
12
R
A3024
(210 - 209.97) / 210 x 1E + 06 = 142.857 ppm.
The value for the digital trimming register is:
142.857 / 0.984 = 145.18, rounded to 145 ppm (91 hex).
The Principle of Digital Trimming
With the digital trimming disabled (i.e. digital trimming register
set to 00 hex), the oscillator and the first stages of the divider
chain will run slightly too fast (typ. 210 ppm: ppm = parts per
million), and will generate a 100 Hz signal with a frequency of
typically 100.021 Hz. To correct this frequency, the digital
trimming logic will inhibit every 31 seconds, a number of clock
pulses, as set in the digital trimming register. Since the duration
of 31 seconds corresponds to 1'015'808 oscillator cycles, the
digital trimming has a resolution of 0.984 ppm. In other words,
every increment by 1 of the digital trimming value will slow down
the clock by 0.984 ppm, which permits the accuray of ±0.5 ppm
to be reached. Note that a 1 ppm error will result in a 1 second
difference after 11.5 days, or a 1 minute difference after 694
days! The trimming range of the A3024 is from 0 to 251 ppm.
The 251 ppm correction is obtained by writing 255 (FFhex) into
the digital trimming register.
Time Correction with Change of Temperature
If the mean temperature on site is known to be 45 °C, the
frequency error determined at room temperature has to be
modified, using the graphs or the equation on Fig. 5.
2
Df/f = -0.038 x (45 - 25) = 15.2 ppm
O
The trimming value for 45 C will be:
(142.857 ppm - 15.2 ppm) / 0.984 = 129.73, rounded to 130 (82 hex).
12 / 24 Hour Data Format
The A3024 can run in 12 hour or 24 hour data format. On
initialisation the 12/24 hour bit ad addr. 00 bit 4 is cleared putting
the A 3024 in 24 hour data format. If the 12 hour data format is
required then bit 4 at addr. 00 must be set. In the 12 hour data
format the AM/PM indicator is the MSB of the hours register
addr. 23 bit 7. A set bit indicates PM. When reading the hours in
the 12 hour data format software should mask the MSB of the
hours register. In the 24 hour data format the MSB is always
zero.
The internal clock registers change automatically between 12
and 24 hour mode when the 24/12 hour bit is changed. The
alarm hours however must be rewritten.
How to Determine the Digital Trimming Value
The value to write into the digital trimming register has to be
determined by the following procedure:
1. Initialise the A3024 by writing a 1 and then a 0 into the
"Initialisation Bit" of the status register 2 (addr. 02 hex, bit 4).
This activates the frequency tuning mode in status register 0
(addr. 00 hex, bit 1) and clears the other status bits.
2. Write the value 00 hex into the digital trimming register
(addr. 10 hex). From now, the IRQ output (open drain) will
deliver the 100 Hz signal, which has a 20% duty cycle.
3. Measure the duration of 21 pulses at the IRQ output, with the
trigger set for the falling edge. It is possible also to divide the
IRQ frequency by 21, using a TTL or CMOS external circuit.
4. Compute the frequency error in ppm:
6
210 ms - measured value in ms
x 10
freq. error =
210 ms
5. Compute the corrective value to write into the digital
trimming register.
Digital trimming value = frequency error / 0.984
6. Write this value into the digital trimming register.
7. Switch off the frequency tuning mode in status 0 (addr. 00
hex, bit 0 set to 0).
The Real Time Clock circuit will now run accurately at an
operating temperature equal to the calibration temperature. If
the operating temperature differs from the one at calibration
time, the graphs shown on Fig. 4 and 5 will help in determining
the definitive value. If the mean operating temperature of the
equipment is not known at calibration time, the equipment user
will do the final correction with a software provided by the
system designer. To avoid the calibration procedure, it is
possible also to set the digital trimming register to 210 (D2 hex)
as a standard starting value, and let the final equipment user
perform the final adjustment on site, which will take the real
temperature into account.
Test
From the various test features added to the A3024 some may be
activated by the user. Table 6 shows the test bits. Table 10
shows the three available modes and how they may be
activated.
The first accelerates the incrementing of the parameters in the
reserved clock and timer area by 32.
The second causes all clock and timer parameters, in the
reserved clock and timer area, to be incremented in parallel at
100 Hz with no carry over, ie. independently of each other.
The third test mode combines the previous two resulting in
parallel incrementing at 3.2 kHz.
While test bit 1 is set (addr. 00 hex, bit 7) the digital trimming
action is disabled and no pulses are removed from the divider
chain. Test bit 0 (addr. 00 hex, bit 6) can be combined with digital
trimming (see section "Frequency Tuning"). To leave test, the
test bits (addr. 00 hex, bits 6 and 7) must be cleared by software.
Test corrupts the clock and timer parameters and so all
parameters should be re-initialised after a test session.
Test Modes
Addr.
Addr.
00hex bit 7 00hex bit 6
Time Correction at Room Temperature
Let us consider that the duration of 21 pulses of the IRQ signal
is 209.97 ms at room temperature.
The frequency error is:
0
0
1
0
1
0
1
1
Function
Normal Operation
Acceleration by 32
Parallel increment of all clock and timer
parameters at 100 Hz with no carry over;
dependent on the status of bit 3 at
address 00 hex
Parallel increment of all clock and timer
parameters at 3.2 kHz with no carry
over; dependent on the status of bit 3 at
address 00 hex
Table 10
13
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A3024
Battery or Supercap Connection
Note : The diodes must have a
forward voltage drop of less than
0.3 V. BAT 85 s are recommended.
VDD
Power fail
(low for standby)
PF
VDD
A3024
+
or
+
Battery
Supercap
VSS
VSS
Fig. 11
Typical Applications
A 3024 Interfaced with Intel CPU (RD and WR pulse)
Address
Address Bus 0 - 7
Latch
A0
A/D Bus 0 - 7
CPU
Address Bus A8 - A15
to other
peripherals
and
memory
Decoder
WR
RD
CS
RD
WR
A/D
D 0-7
A3024
Fig. 12
A 3024 Interfaced with Motorola CPU (DS or RD pin tied to CS, and R/W)
Data Bus
CPU
Address Bus
to other
peripherals
and
memory
A0
Decoder
R/W
DS
RD
CS
A/D WR
AD 0-7
A3024
Fig. 13
14
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A3024
Process Application
Oscillator Layout
VDD
VSS
Temperature
sensor
XIN
XOUT
Controller
Solenoid
valve
Fig. 14
Fig. 15
- The formula in Fig. 5 is used by software to continually update
the digital trimming register and so compensate the A3024 for
the ambient temperature.
- The timer is used to measure the duration the valve is on.
- The alarm feature is used to turn the controller power on and
off at the time programmed by software. The A3024 pulls IRQ
active low on an alarm even in standby and thus can control
the power on/off switch for the controller.
- The user RAM provides the controller with non volatile RAM
for vital parameters. For example :
1) the total on time for the valve to enable software to
compute energy usage and also to identify when service is
needed
- 3 bytes
2) average on time for the valve
- 2 bytes
3) maximum temperature ever encountered together with the
time and date
- 6 bytes
4) date of last service and service man’s ID
- 4 bytes
5) identification code for the controller
- 1 byte
External Clock
An external signal generator can be used to drive the divider
chain of the A 3024. Fig. 16a and 16b show how to connect the
signal generator.
Signal Generator
XIN
1- 2 V peak to peak
A3024
XOUT
VSS
Crystal Layout
Fig. 16a
Note : The peak value of the signal provided by the signal
generator should not exceed 2 V on XOUT.
In order to ensure proper oscillator operation we recommend
the following standard practices:
- Keep traces as short as possible.
- Use a guard ring around the crystal.
Fig. 15 shows the recommended layout.
XIN
0 - 5.5 V
1)
100 kW
A3024
XOUT
1)
56 kW
VSS
1)
indicative values
Fig. 16b
Note : The peak value of the signal provided by the signal
generator should not exceed 2 V on XOUT.
15
R
A3024
Package and Ordering Information
Dimensions of 20-Pin SOIC Package
Dimensions in mm
D
h x 45°
a
A
C
L
A1
H
20
19
18
13
12
11
A
A1
B
C
D
E
e
H
h
L
a
Min. Nom. Max.
2.35
2.65
0.10
0.30
0.33
0.51
0.23
0.32
12.60
13.00
7.40
7.60
1.27
10.00
10.65
0.25
0.75
0.40
1.27
0°
8°
E
1
2
3
8
9
e
10
B
Fig. 17
Dimensions of 20-Pin Plastic DIP Package
E
D
A2
A
L
A1
b
b2
b3
c
eA
eB
e
D1
20 19 18 17 16 15 14 13 12 11
E1
1
2
3
4
5
6
7
8
9
10
Dimensions in mm
Min. Nom. Max.
A
5.33
A1 0.38
A2 2.92 3.30 4.95
b
0.35 0.46 0.56
b2 1.14 1.52 1.78
b3 0.76 0.99 1.14
c
0.20 0.25 0.36
D
24.89 26.16 26.92
E
7.62 7.87 8.26
E1 6.09 6.35 7.11
e
2.54
eA
7.62
eB
10.92
L
2.92 3.30 3.81
Fig. 18
16
R
A3024
Ordering Information
When ordering, please specify the complete part number.
Part Number
Package
A3024SO20B
20-pin SOIC
A3024SO20A
20-pin SOIC
A3024DL20A 20-pin plastic DIP
Delivery Form
Tape & Reel
Stick
Stick
Package Marking
(first line)
A3024 20S
A3024 20S
A3024 20PI
EM Microelectronic-Marin SA cannot assume responsibility for use of any circuitry described other than circuitry entirely embodied in an
EM Microelectronic-Marin SA product. EM Microelectronic-Marin SA reserves the right to change the circuitry and specifications without
notice at any time. You are strongly urged to ensure that the information given has not been superseded by a more up-to-date version.
Ó 2002 EM Microelectronic-Marin SA, 03/02, Rev. E/384
EM MICROELECTRONIC-MARIN SA, CH-2074 Marin, Switzerland, Tel. +41 - (0)32 75 55 111, Fax +41 - (0)32 75 55 403