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DS1075M-80

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DS1075
10 of 18
Figure 9
POWER-ON RESET
When power is initially applied to the device supply pin, a power-on reset sequence is executed, similar
to that which occurs when the device is restored from a power-down condition. This sequence comprises
two stages, first a conventional POR to initialize all on-chip circuitry, followed by a stabilization period
to allow the oscillator to reach a stable frequency before enabling the outputs:
1. Initialize internal circuitry.
2. Enable internal oscillator and/or OSCIN buffer.
3. Set M and N to maximum values.
4. Wait approximately 256 cycles of MCLK for the oscillator to stabilize.
5. Load M and N programmed values from EEPROM.
6. Enable OUT0 (assuming EN0=0).
7. Enable OUT.
Figure 10
PROGRAMMING
Normally when power is applied to the supply voltage pin the device will enter its normal operating mode
following the power-on reset sequence. However the device can be made to enter a programming mode if
a pull-up resistor is connected between IN/OUT and the supply voltage pin, prior to power-up. The
method used for programming is a variant of the 1-Wire
™ protocol used on a number of Dallas
Semiconductor products.
DS1075
11 of 18
HARDWARE
The hardware configuration is shown in the diagram. A bus master is used to read and write data to the
DS1075’s internal registers. The bus master may have either an open-drain or TTL-type architecture.
Figure 11
Programming mode is entered by simply powering up the DS1075 with a pull-up of approximately 5KW.
This will pull the IN/OUT pin above V
IH
on power-up and initiate the programming mode, causing the
DS1075 to internally release the IN/OUT pin (after t
POR
), and allow the pull-up resistor to pull the pin to
the supply rail and await the Master Tx Reset pulse (see diagram).
NOTE:
To ensure normal operation any external pull-up applied to IN/OUT must be greater than 20KW in value.
This will cause the IN/OUT pin to remain below V
IH
on power-up, resulting in normal operation at the
end of t
STAB
.
Figure 12
DS1075
12 of 18
TRANSACTION SEQUENCE
The sequence for accessing the DS1075 via the 1-Wire port is as follows:
Initialization
Function Command
Transaction/Data
INITIALIZATION
All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence
consists of a reset pulse transmitted by the bus master followed by a presence pulse(s) transmitted by the
DS1075. The presence pulse lets the bus master know that the DS1075 is present and is ready to operate.
Figure 13
FUNCTION COMMANDS
Once the bus master has detected a presence, it can issue one of the four function commands. All
Function Commands are eight bits long, and are written lsb first. A list of these commands follows:
Write DIV Register [01H]
This command allows the bus master to write to the DS1075’s DIV register.
Read DIV Register [A1H]
This command allows the bus master to read the DS1075’s DIV register.
Write MUX Register [02H]
This command allows the bus master to write to the DS1075’s MUX register.
Read MUX Register [A2H]
This command allows the bus master to read the DS1075’s MUX register.
TRANSACTION/DATA
Immediately following the Function Command, the nine data bits are written to or read from the DS1075.
This data is written/read lsb first. The following diagrams illustrate the timing. Once data transfer is
complete a new transaction sequence can be started by re-initializing the device. Therefore to program
both the DIV and MUX registers two complete transaction sequences are required.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18

DS1075M-80

Mfr. #:
Buy DS1075M-80
Manufacturer:
Maxim Integrated
Description:
Programmable Oscillators
Lifecycle:
New from this manufacturer.
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