Nokia 9000i Service Manual page 63

After Sales
Technical Documentation
Interface to the MCU is done with 8 bit data bus, 5 bit lower address bus,
4 bit upper address bus, RSTROBEX, WSTROBEX, IRQX and NMI. ASIC
is in the same memory space as MCU memories. There is also
MBUS/RBUS detector and netfree counter on the ASIC. Netfree interrupt
IRQX occurs if no activity is detected in MBUS in about 3 ms.
netfree counter cannot be used in the CMT because RBUS data is seen at the same pin .
NMI is used to wake up the MCU from sleep mode.
MCU and DSP communicate through ASIC. ASIC has an MCU mailbox
and a DSP mailbox. MCU writes data to DSP mailbox where DSP can only
read the incoming data. In MCU mailbox the data transfer direction is the
opposite. The size of the mailbox is 64 * 8 bit.
MCU and User Interface (keyboard and display) communication is
controlled through the ASIC. COL(3:0) are used as column lines in
keyboard. UIF(5:0) are used as row lines They are also multiplexed with
display driver control signals.
When a key is pressed the ASIC gets a reset from row and starts
scanning. One column at the time is written to low and rows are used to
read which key it was. Row lines and UIF6 are used for display driver
control. UIF(3:0) are used as 4 bit parallel data bus for the LCD driver.
UIF4 is used as read/write strobe, UIF5 to select data or instruction
register and UIF6 as enable strobe.
The SIM interface is the electrical interface between the SIM (the smart
card used in the GSM and PCN applications) and the MCU via the ASIC.
ASIC converts the serial data received from the SIM to parallel data for
MCU and converts parallel data from MCU to serial mode for the card.
The SIM interface also takes care of the power up and down procedure to
the card in addition to frame and parity error checking. The
communication between card and ASIC is asyncronous and half
duplex.Four signals are used between the ASIC and the SIM card:
SIMDATA, SIMCLK,SIMRESET and VSIM. The nominal clock frequency is
3.25 MHz. When there is no data transfer between the SIM card and the
CMT the clock can be reduced to 1.625 MHz. Some SIM cards also allow
the clock to be stopped in that mode. Supply voltage VSIM can be
switched off by the ASIC. The supply voltage range is 4.65–4.95 V. The
card detect input of the ASIC is connected to BTYPE pin and when the
battery is removed the ASIC will drive the SIM down.
The interface to the DSP is done using 6 bit address bus, 16 bit data bus,
IOX and RWX lines. Data bus is latched using IOX, address bus is not.
The ASIC also generates interrupt INT0 when an edge occurs in DBUS
line (if the mask bit is off). INT1 is used as RX interrupt and as MFI
modulator interrupt to the DSP.
Viterbi is used to perform GSM/PCN convolutional decoding and bit
detection according to the Viterbi algorithm. It can be controlled and
accessed thoroughly by the DSP.
Original, 08/96
RAE/RAK–1N
Baseband
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