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unrznbl, 02/11/2019 03:44 AM


MT6235 Radio Interface Control

facts adapted Section 9, page 446 of MT6235 GSM/GPRS Baseband Processor Data Sheet Revision 1.02

The interface is composed of the Baseband Serial Interface (BSI), Baseband Parallel Interface (BPI), Automatic Power Control (APC), Automatic Frequency Control (AFC), APC-DAC and AFC-DAC.

Baseband Serial Interface (BSI)

BSI controls external radio components. A 3-wire serial bus sends data to RF circuits for PLL frequency change, reception gain setting and other radio control purposes. BSI data registers are double-buffered the same as TDMA event registers. Data written into the write buffer is transferred from the write buffer to the active buffer when a TDMA_EVTVAL signal from the TDMA timer is pulsed.

Each data register BSI_Dn_DAT is linked with one data control register BSI_Dn_CON. n denotes an index. Each data control register is linked to which events trigger the download process of the word in register BSI_Dn_DAT. This is signaled by TDMA_GSISTRn generated by the TDMA timer. The word and its length in bits is downloaded via the serial bus. An event is triggered when the IMOD flag is set to 1. This provides immediate download process without software programming the TDMA timer.

For the same BSI event, if more than one data word needs to be downloaded, the word with the lowest address among them is downloaded first followed by the next lowest, etc.

Depending on the word length and clock rates the download time will vary. The developer should ensure enough time is given for each subsequent event. If the download of an earlier event is not finished before the next event arrives the next event is ignored.

This block has four output pins: BSI_CLK - the output clock, BSI_DATA - serial data output, BSI_CS0 and BSI_CS1 - select pins for two external components. BSI_CS1 is multiplexed with another function. Refer to CPIO information for more details.

It is possible to write values directly to BSI_CLK, BSI_DATA and BSI_CS by programming the BSI_DOUT register. This supports bi-directional read and write operations to/from the RF chip. Data from the RF chip is read by the BSI_DIN register. BSI_DATA is bi-directional if the physical interface with the RF chip consists of 3 wires. BSI_IO_CON register must be set before the interface can interact as a 3-wire interface. If the RF chip has a 4-wire interface then the additional signal path can be dealt with via GPIO.

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Updated by unrznbl about 5 years ago · 2 revisions

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