Calypso Digital Baseband

The Calypso Digital Base Band chip is a popular DBB implementation for inexpensive feature phones.

The register-level manuals seem to have leaked at some point and are available from
at and

As is currently suffering legal battles due to Microsoft stupidity,
you can use /


  • Calypso G2 C035
  • Calypso G2 C035 Lite (D751749GHH)
    • Like C035, only 256kBytes of internal memory


More information on the DSP used in the Calypso DBB is available on HardwareCalypsoDSP.


The CPU embedded in the calypso chipset is a ARM7TDMI. Details documents about this CPU is available from the ARM infocenter at "h2. Memory Map

  • nCS0 0x0000'0000 ... 0x007f'ffff (C123: external NOR flash)
  • nCS6 0x0080'0000 ... 0x00bf'ffff (internal SRAM, in case of calypso lite only 256kBytes)
  • nCS1 0x0100'0000 ... 0x017f'ffff (C123: external SRAM)

Integrated Peripherals
TPU (Time Processing Unit) =
  • A programmable micro-engine clocked at GSM quarter-bit clock


  • The UART that is typically connected to a PC or the application processor in a smartphone


  • The UART that is either connected to IRDA or for diagnostics/programming

RIF (Radio Interface)

  • Connects to the synchronous bi-directional BSP (Baseband Serial Port)

DPLL + clock block

  • Generate clocks for DSP, ARM and all peripherals

GEA (GPRS Encryption Algorithm)

  • Encrypts/Decrypts data according to the proprietary GEA algorithm

Watchdog timer ===
Interrupt Controller ===

Memory interface (SRAM/ROM) ===
DMA controller ===
  • Only usable for UART and RIF, can only DMA to small API RAM memory region

SIM card controller

  • Connects to the SIM card socket in the phone

TSP controller (Time Serial Port)

  • Controls the TSP, which controls the sequencing of all external peripherals like ABB, RF chip, RF PA, Antenna Switch

RTC clock

  • A pretty standard realtime clock

ULPD (Ultra Low Power Device)

  • Responsible for enabling the phone to go to lowest-possible power mode while IDLE, but still waking up at the right point to receive important data (like paging channel) from the BTS

I2C Master controller

  • Typically connects to external peripherals like LCD (if any)
The controller has two oddities:
  • It assumes that the peripheral has an address byte. If your peripheral doesn't, you have to
    write the first byte into the address register and not the FIFO
  • You cannot under-fill the FIFO, i.e. if you write 8 bytes into the 16byte deep fifo, the controller
    will transmit 16 bytes rather than 8. Therefore, always limit the FIFO depth to your write size!
    More details about this can be seen at HardwareCalypsoI2CFIFO"httpinfocenterarmcomhelpindexjsp.

SPI Master controller

  • Connects to USP of ABB and possibly other external peripherals

TIMER1 / TIMER2 general purpose timers

The timer input clock is not mentioned in the data sheet. It seems to be 13MHz / 32, i.e. 406.25kHz

PWL (PWM for Light)

  • connected to the screen/keypad backlight

PWT (PWM for Tones)

  • connected to a buzzer for ringtone generation

JTAG Interface

The Calypso has an ARM7TDMI JTAG interface, which is exposed on phones like the Motorola [[MotorolaC115|C115] [wikiMotorolaC155 C155] [wikiSonyEricssonJ100i Sony Ericsson J100i] and the [wikiPirelliDPL10 Pirelli DP-L10]].
With standard ARM JTAG debuggers like OpenOCD, halting the core does not work out-of-the-box, because ARM instruction 0xb needs to be executed first (which is an proprietary extension to the ARM7TDMI TAP-Controller). It is unclear what this instruction does exactly.
The OpenOCD configuration file along with the corresponding svf-file is attached to this page.

Debug traces

The chip has very tiny debug traces on a small flex-pcb around the 4 sides of the chip.
Which trace goes to which ball can be seen on this scan:

openocd_calypso.cfg - OpenOCD configuration for the Calypso (997 Bytes) steve-m, 01/31/2012 01:29 PM

calypso_magic.svf - Calypso "magic" SVF (172 Bytes) steve-m, 01/31/2012 01:29 PM