CMAXQUSB datasheet(3/14 Pages) MAXIM

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Evaluate: MAX6889/MAX6892

MAX6889 Evaluation Kit/

Evaluation System

When a PO_ signal is asserted, several actions may

occur. The corresponding PO_ pin can be driven to a

high or low logic level. The pin driver can be configured

as open-drain or as a push-pull output.

User EEPROM writes may optionally be locked out when

the PO_ is asserted.

The MARGIN signal allows user system testing, by

forcing the PO_ signal to hold its previously determined

state. It is expected that MARGIN will be high during

normal operation.

Watchdog Timer Tab

The watchdog timer asserts a fault condition after a period

of time, unless the timer is periodically reset by an input

pin being toggled (Figure 6).

During normal operation, an enabled watchdog timer

must be serviced by toggling a GPI pin periodically.

Typically an external piece of firmware would service

the watchdog timer by toggling a GPI pin inside a loop,

and watchdog timer assertion would be configured to

drive a PO_ output pin. Any software defect that halts the

firmware then causes the watchdog timer to assert.

The initial timeout period can be set to a longer value,

to allow time for software initialization. Alternatively,

the watchdog timer can be held in reset by an optional

“clear” input. Refer to the MAX6889 data sheet for more

information about watchdog timer operation.

Registers Tab

The

Registers tab displays the volatile working registers

of the MAX6889 (Figure 7). Pressing

Refresh reads and

displays all register values. Individual register bytes can

be modified by selecting the appropriate grid cell and

typing zero-x prefix “0x” followed by two hexadecimal

digits 0–9/A–F. If

Options menu item Confirm REG write

when editing is checked, a dialog box appears to confirm

each byte written in this manner.

At power-up, the MAX6889 automatically loads its regis-

ters from the configuration EEPROM. To store the active

Commit to EEPROM.

disk for later retrieval, using the

Load from File and Save

to File buttons.

EEPROM Tab

The

EEPROM tab displays the nonvolatile EEPROM

memory of the MAX6889 (Figure 8). Pressing

Refresh

reads and displays the selected EEPROM page. Individual

memory bytes can be modified by selecting the appropri-

ate grid cell and typing zero-x prefix “0x” followed by

two hexadecimal digits 0–9/A–F. If

Options menu item

Confirm EEPROM write when editing is checked, a

dialog box appears to confirm each byte written in this

manner.

EEPROM values can optionally be stored into a text file

on disk for later retrieval, using the

Load from File and

Save to File buttons.

Detailed Description of Hardware

The MAX6889 (U1) is surrounded by breakout header pins

H1–H4. Capacitors C1 and C2 bypass the power supply.

The user power-supply inputs IN1–IN8 are bypassed by

capacitors C3–C10.

Connector P1 mates with the CMAXQUSB module,

which enables communication with software running

on a PC (there are SCL/SDA pullup resistors on the

module board). As a convenience, the module also

provides power to U1 through jumper JU1. This same

power supply also powers most of the EV kit LEDs

through jumper JU22.

Programmable outputs PO1–PO10 drive optional

active-low LED indicators. When the LED is on, that

indicates that the corresponding PO output is low.

Capacitors C11 and C12 are left open when used with

the MAX6889. These component sites are provided to

support the MAX6892.

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