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KS152JB Universal Communications Controller
Technical Specifications
Kawasaki LSI USA, Inc. Page 93 of 120 Ver. 0.9 KS152JB2
As shown in Figure above, the Receive Valid interrupt can be signalled either by the RFNE flag
(Receive FIFO Not Empty), or by the RDN flag (Receive Done). Which one of these flags causes
the interrupt depends on the setting of the DMA bit in the SFR named TSTAT.
DMA = 0 means the DMA hardware is not configured to service the GSC, so the CPU will service
it in software in response to the Receive FIFO not being empty. In that case, RFNE generates the
Receive Valid interrupt.
DMA = 1 means the DMA hardware is configured to service the GSC, in which case the CPU
need not be interrupted till the receive is complete. In that case RDN generates the Receive Valid
interrupt.
Similarly the Transmit Valid interrupt can be signalled either by the TFNF flag (Transmit FIFO
Not Full), or by the TDN flag (Transmit Done), depending on whether the DMA bit is 0 or 1.
Note that setting the DMA bit does not itself configure the DMA channels to service the GSC.
That job must be done by software writes to the DMA registers. the DMA bit only selects whether
the GSCRV and GSCTV interrupts are flagged by a FIFO needing service or by an “operation
done” signal.
The Receive and Transmit Error interrupt flags are generated by the logical OR of a number of
error conditions, which are described in Section 3.6.5.
Each interrupt is assigned a fixed location in Program Memory, and the interrupt causes the CPU
to jump to that location. All the interrupt flags are sampled at S5P2 of every machine cycle, and
then the samples are sequentially polled during the next machine cycle. If more than one interrupt
of same priority is active, the one that is highest in the polling sequence is serviced first. The inter-
rupts and their fixed locations in Program Memory are listed below in the order of their polling
sequence
Table 14:
Interrupt Location Name
IE0 0003H External Interrupt 0
GSCRV 002BH GSC Receive Valid
TF0 000BH Timer 0 Overflow
GSCRE 0033H GSC Receive Error
DMA0 003BH DMA channel 0 Done
IE1 0013H External interrupt 1
GSCTV 0043H GSC Transmit Valid