DS2790 Maxim Integrated Products, DS2790 Datasheet - Page 12

• Manufacturer Part Number: DS2790
• Description: Programmable 1-Cell Li-Ion Fuel Gauge and Protector
• Manufacturer: Maxim Integrated Products

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Activating the JTAG interface and loading the Test Access Port (TAP) with the system programming instruction
invokes the bootstrap loader for use over the JTAG interface. Setting the SPE bit to 1 during reset through the
JTAG interface executes the bootstrap-loader-mode program that resides in the utility ROM. When programming is
complete, the bootstrap loader can clear the SPE bit and reset the device, allowing the device to bypass the utility
ROM and begin execution of the application software.
Performing a program request over the 2-wire interface also invokes the bootstrap loader. The user must
successfully complete a password match (If PWL = 1). The bootstrap loader functions are then fully supported over
the 2-wire interface. When programming is complete, the exit loader function is used to reset the DS2790 and
begin execution of the application software.
The following bootstrap loader functions are supported:
·
·
·
·
·
·
In-Application Programming
The in-application programming feature allows the microcontroller to modify its own EEPROM program memory.
This allows on-the-fly software updates in mission-critical applications that cannot afford downtime. Alternatively, it
allows the application to develop custom loader software that can operate under the control of the application
software. The utility ROM contains firmware-accessible EEPROM programming functions that erase and program
EEPROM memory. These functions are described in detail in the MAXQ Family User's Guide: DS2790
Supplement.
SYSTEM TIMING
The DS2790 generates its 1MHz instruction clock (OSCI) internally. This quick starting oscillator is used for
instruction fetch and execution by the MAXQ20 core.. The analog oscillator (OSCA) is a band-gap based RC
oscillator that is trimmed to better than 2% accuracy. The analog clock runs independent of OSCI and serves as
the clock source for the ADC, watchdog timer, interval timer, and 2-wire timeouts.
OSCI is enabled through either a system interrupt or system POR and disabled through a system STOP. A voltage
brown out detection circuit disables OSCI if VDD falls below V
waits t
/ Counter (TMOD), or by the protection circuitry (PMM[1:0]).
Figure 5. System Clocks
4
Information Commands
Load EEPROM Code and Data
Dump EEPROM Code and Data
CRC EEPROM Code and Data
Verify EEPROM Code and Data
Erase EEPROM Code and Data
Interrupt
SU:OSCI
PMM.0
PMM.1
TMOD
STOP
EWDI
EWT
POR
before re-enabling OSCI. OSCA is enabled by the Watchdog Timer signals EWDI or EWT, the Timer
Enable
OSCA
Enable
OSCI
EN
EN
EN
DS2790 Programmable 1-Cell Li-Ion Fuel Gauge and Protector
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Oscillator
Brown Out
Oscillator
Detector
70kHz
1MHz
BO
VDD < V
. Once VDD raises above V
BO
CLR
Brown Out
CLK
D
Hysteresis
(t
SU:OSCI
Q
)
BO
, a hysteresis circuit
OSCI
OSCA