PEB 20560
Functional Block Description
Semiconductor Group
2-6
2003-08
2.1.2.4
SACCO
The SACCO (Special Application Communication Controller) is a high level serial
communication controller consisting of two independent HDLC-channels (A
+
B). It is a
derivative product of the Siemens SAB 82525 (HSCX).
The SACCO essentially reduces the hardware and software overhead for serial
synchronous communication. SACCO channel A can be multiplexed by the D-channel
arbiter to serve multiple subscribers.
In the following section one SACCO channel is described referring to as “SACCO”.
2.1.2.4.1
Block Diagram
The SACCO (one channel) provides two independent 64-byte FIFOs for receive and
transmit direction and a sophisticated protocol support. It is optimized for line card
applications in digital exchange systems and offers special features to support:
– Communication between a line card and a group controller
– Communication between terminal equipment and a line card
2.1.2.4.2
All registers and the FIFOs are accessible via the DOC parallel
μ
P-interface. The FIFOs
allocate an address space of 32 bytes each. The data in the FIFOs can be managed by
the CPU- or a DMA-controller.
To enable the use of block move instructions, the top of FIFO-byte is selected by any
address in the reserved range.
Parallel Interface
Interrupts
The SACCO indicates special events by issuing an interrupt request. The cause of a
request can be determined by reading the interrupt status register ISTA_A/B or
EXIR_A/B. The related register is flagged in the top level ISTA (refer to
Figure 3-1
).
Three indications are available in ISTA_A/B, another five in the extended interrupt
register EXIR_A/B. An interrupt which is masked in the MASK_A/B is not indicated in the
top level register and the INT-line is not activated. The interrupt is also not visible in the
local registers ISTA_A/B but remains stored internally and will be indicated again when
the corresponding MASK_A/B-bit is reset.
The SACCO-interrupt sources can be splitted in three logical groups:
Receive interrupts
(RFS, RPF, RME, EHC)
Transmit interrupts
(XPR, XMR)
Special condition interrupts
(XDU/EXE, RFO)
For further information refer to
chapter 3.1.4.1
(Data Transmission in Interrupt Mode)
and
chapter 3.1.4.3
(Data Reception in Interrupt Mode).