Siemens ERTEC 200P, Руководство пользователя

Страница: 125 / 501

Copyright © Siemens AG 2016. All rights reserved 125 ERTEC 200P-2 Manual
Technical data subject to change Version 1.0
2.3.4.2.2 DMA with UART Interface
As the DMA request signals available at UART1…4 are not suitable for GDMA operation,
internal status signals are used from the FIFO controller and sent to the GDMA as DMA
request signals. The signals for controlling the transmitter and receiver separately over
one GDMA channel each are as follows:
UART_RX-FIFO not empty:
The RX FIFO contains at least one character and is not empty. As the UART can-
not know when the last character (byte) was read in, the GDMA must oper-
ate in SINGLE-byte access mode (AHB). 1 to 65536 characters can therefore be
transferred per DMA request; the job consists of a transfer entry.
UART_TX-FIFO half-full or less:
The TX FIFO is at least half empty and therefore has space for 8 characters
(bytes). The GDMA must not operate in more than INCR8-byte access mode
(AHB) to ensure that there is no FIFO overrun. When GDMA write access is set to
HOLD Address, the bytes are
always transferred to the TX FIFO with SINGLE-
byte access irrespective of the access mode. INCR8-byte access mode is there-
fore only effective for reading data (e.g. from RAM). If the transfer length is not
modulo 8, the remaining characters are read by the GDMA controller with the
INCR burst byte (undefined length) and transferred to TX FIFO with SINGLE-
byte. 1 to 65536 characters can therefore be transferred per DMA request; the job
consists of a transfer entry.
Note: Unlike with frame-oriented transfer over SPI, the GDMA cannot wait for TX FIFO
Empty (TFE) to continue writing the TX FIFO: because of GDMA latency, this could lead
to a TX FIFO underrun and the UART serial data stream could not be maintained. It is
however possible with a GDMA-SPI interconnect as there is a longer pause between the
SPI frames to be transmitted.
2.3.4.3 GDMA-IP Bugs
JOB_Reset:
JOB_RESET for the last job (ERTEC 200P: JOB31) does not work reliably. With
JOB31, JOB_RESET does not delete all information for the last job. This means that
the information that the JOB has been interrupted and needs to be continued in the
JOB STACK has not been deleted either. A new JOB configuration is therefore not ef-
fective.
With ERTEC 200P, JOB31 should not be used as HW-JOB; otherwise, the following
error description and workaround apply. JOB31 could be used as SW-JOB if the SW
does not interrupt it with JOB_Reset.
Error description: JOB31 is to be canceled and restarted
1. JOB31 is disabled with
a) JOB_EN = 0 (bit 1 in GDMA_JOB31_CTRL) or
b) HW_DMA_REQ_i = 0 (GDMA input signal)
2. JOB31 is reset by JOB_RESET = 1 (bit 5 in GDMA_JOB31_CTRL)
3. JOB31 is enabled, but not started. -> GDMA continues JOB31 from where it
was interrupted, i.e. deleting does not work for JOB31 in the GDMA