EM6517 datasheet(29/64 Pages) EMMICRO

29 / 64 page

EM6517

03/02 REV. C/448

 2002, EM Microelectronic-Marin SA

www.emmicroelectronic.com

Serial (Output) Write Buffer - SWB

The EM6517 has simple Serial Write Buffer which outputs serial data and serial clock.

Serial Write Buffer clock frequency is selected by bits SWBFSel0 and SWBFSel1 in RegSWBCntl register. The

possible values are 1kHz (default), 2kHz, 8kHz or 16kHz.

The signal TestVar[3], which is used by the processor to make conditional jumps, indicates "Transmission

finished" in automatic send mode or "SWBbuffer empty" in interactive send mode. In interactive mode,

TestVar[3] is equivalent to the interrupt request flags stored in RegIRQ[i] registers : it permits to recognize the

interrupt source. (See also the interrupt handling section 13 for further information). To serve the "SWBbuffer

empty " interrupt request, one only has to make a conditional jump on TestVar[3].

The SWB data is output on the rising edge of the clock. Consequently, on the receiver side the serial data can

be evaluated on falling edge of the serial clock edge.

Normally the Clock and the Data output terminals are always driven to ‘0’ outside a SWB data transfer. With a

metal option one can put the Data output, the Clock output or both into a high impedance state outside of a SWB

transfer. Refer to 19.1.4 for the mask settings. The timing going into high impedance state into SWB transfer

and back into high impedance is depending on the selected mode, interactive or automatic.

Figure 22. Serial Write Buffer Architecture

Size[5:0]

Addr. Counter

RAM

SW B buffer

SW Bauto

SW BStart

SW BFSel0,1

Control

Logic

Shift register

DB[3:0]

Clk

Mux

SW B clock

SW B data

TestVar3

SW B buffer

IRQ (only in

interactive

SWB has two operational modes, automatic mode and interactive mode.

9.1 SWB Automatic send mode

Automatic mode enables a buffer on a predefined length to be sent at high transmission speeds up to ck[15]

(16kHz). In this mode user prepares all the data to be sent (minimum 8 bits, maximum 256 bits) in the RAM.

The user then selects the clock speed, sets the number of data nibbles to be sent, selects automatic

transmission mode (SWBAuto bit set to 1) and enters STANDBY mode by executing a HALT instruction. Once

the HALT instruction is activated the SWB peripheral module sends the data in register RegSWBuff followed by

the data in the RAM starting at address 00 up to the address specified by the bits size[5:0] located in the

RegSWBSizeL, RegSWBSizeH

registers.

EM6517 Datasheet(PDF) 29 Page - EM Microelectronic - MARIN SA

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