Micrel, Inc.
MIC2555
SCL, SDA
GPIO_1_TX, GPIO_0_RX, GPIO_2
The serial clock (SCL) and serial data (SDA) signals
implement a two-wire I2C serial bus for control of the
GPIO_0, GPIO_1, and GPIO_2 are general purpose
I/Os that can be used as data ports or interrupt sources
for the system controller, display drivers or power
switches for actuators or annunciators.
MIC2555. As with all I2C busses the MIC2555 shares a
common external pull-up resistor on each line.
These GPIO have open drain outputs capable of sinking
at least 10 mA, can be wire ORed together, and may be
pulled above the MIC2555’s operating supply voltage,
but not beyond the 6V absolute maximum allowed. As
logic inputs, the GPIO logic thresholds are standard
CMOS thresholds set by VDD_LGC voltage.
INT/
The interrupt (INT/) pin is asserted while an interrupt
condition exists. It is an open drain output so that it can
be wire-ORed with other interrupt signals, and requires
an external pull-up resistor to provide a logic output. The
pull-up voltage must not be greater than VBAT
.
The GPIO Input Register is a read-only register and
shows real time status of the GPIOs, independent of
other I/O settings. The GPIO Output Register holds the
desired output value for each I/O. Each I/O can act as an
independent interrupt source and can be programmed
for triggering on T Æ F, F Æ T, or both transitions
simultaneously.
ADR0
Because some systems may have more than one
transceiver on the I2C bus, OTG Transceivers have
been assigned four I2C Address locations by convention.
MIC2555 address: 01011xxb (Bit order: A6 Æ A0)
The GPIO pins serve double duty as active signal pins
when called into action by the appropriate control bit:
The ADR0 pin and MIC2555’s ‘dash number’ control the
‘xx’ of MIC2555’s address, where –0 or –1 specifies the
higher order bit’s value:
GPIO_0 = Secondary UART Receive input.
GPIO_1 = Secondary UART Transmit output.
GPIO_2 = External charge pump oscillator input.
Part Number
Address Range
MIC2555BML-0
MIC2555BML-1
0x
1x
Audio mode:
D+
Stereo
These are generally agreed
D-
Where x = the state of ADR0
upon, but are not
D+
D-
Mono
Mic
D+, D-
mandatory.
The data plus (D+) and data minus (D-) pins output the
USB data signals. When operating as a non-USB
transceiver, the role of D+, D- change:
UART mode:
D+ = RXD
D
-
= TXD
M9999-060805
(408) 955-1690
June 2005
19
MICREL [ MICREL SEMICONDUCTOR ]
