EM6605 EM Microelectronic, EM6605 Datasheet - Page 24

• Manufacturer Part Number: EM6605
• Description: 4 bit Microcontroller
• Manufacturer: EM Microelectronic

EM6605
11.1. 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 *f1). 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 (AutoSWB 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 SWBuff 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 LowSWB, HighSWB
registers.
During automatic transmission the general INTEN bit is disabled automatically to prevent other Interrupts to
reset the standby mode. At the end of automatic transmission EM6603 leaves standby mode (INTEN is
automatically Enabled) and sets TestVar[3] high. TestVar[3] = 1 is signaling SWB transmission is terminated.
As soon as SWBAuto is high, the general IntEn flag is disabled until the SWBAuto goes back low.
After automatic SWB transmission INTEN bit becomes active high. Although set to 1 via the Halt instruction the
bit INTEN is disabled throughout the whole SWB automatic transmission. It resumes to 1 at the end of
transmission .
The data to be sent must be prepared in the following order:
First nibble to be sent must be written in the SWBuff register . The other nibbles must be loaded in the RAM from
address 0 (second nibble at adr.0, third at adr.1,...) up to the address with last nibble of data to be send =
"size" address. Max. address space for SWB is 3E ("size" 3E hex) what gives with SWBuff up to 64 nibbles (256
bits) of possible data to be sent. The minimum possible data length we can send in Automatic SWB mode is 8 bits
when the last RAM address to be sent is 00 ("size" = 00)
Once data are ready in the RAM and in the SWBuff, user has to load the "size" (adr. of the last nibble to be send -
bits size[5:0]) into the LowSWB and HighSWB register together with AutoSWB bit = 1.
Now everything is ready for serial transmission. To start the transmission one has to put the EM6603 in standby
mode with the HALT instruction. With this serial transmission starts. When transmission is finished the TESTvar[3]
(can be used for conditional jumps) becomes active High, the AutoSWB bit is cleared, the processor is leaving the
Standby mode and INTEN is switched on.
Figure 13.Automatic Serial Write Buffer transmission
© EM Microelectronic-Marin SA, 02/99, Rev. B/243
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