Maxim Integrated DS33R11 - Manual (Page 42)

DS33R11 Ethernet Mapper with Integrated T1/E1/J1 Transceiver
42 of 344
Both the transmit and receive path of the integrated T1/E1/J1 transceiver also have two HDLC controllers. The
HDLC controllers transmit and receive data through the framer block. The HDLC controllers can be assigned to
any time slot, group of time slots, portion of a time slot or to FDL (T1) or Sa bits (E1). Each controller has 128-byte
FIFOs, thus reducing the amount of processor overhead required to manage the flow of data. In addition, built-in
support for reducing the processor time is required in SS7 applications.
The backplane interface provides a versatile method of sending and receiving data from the host system. Elastic
stores provide a method for interfacing to asynchronous systems, converting from a T1/E1 network to a 2.048MHz,
4.096MHz, 8.192MHz, or N x 64kHz system backplane. The elastic stores also manage slip conditions
(asynchronous interface).
8.1 Processor Interface
Microprocessor control of the DS33R11 is accomplished through the interface pins of the microprocessor port. The
8-bit parallel data bus can be configured for Intel or Motorola modes of operation with the two MODEC[1:0] pins.
When MODEC[1:0] = 00, bus timing is in Intel mode, as shown in
Figure 13-9 and Figure 13-10 . When
MODEC[1:0] = 01, bus timing is in Motorola mode, as shown in Figure 13-11 and Figure 13-12 . The address space
is mapped through the use of 10 address lines, A0-A9. Multiplexed Mode is not supported on the processor
interface. See the timing diagrams in AC Electrical Characteristics in Section
13 for more details.
The Chip Select ( CS) pin must be brought to a logic low level to gain read and write access to the microprocessor
port. With Intel timing selected, the Read ( RD) and Write (WR) pins are used to indicate read and write operations
and latch data through the interface. With Motorola timing selected, the Read-Write (R W) pin is used to indicate
read and write operations while the Data Strobe ( DS) pin is used to latch data through the interface.
The interrupt output pin ( INT) is an open-drain output that will assert a logic-low level upon a number of software
maskable interrupt conditions. This pin is normally connected to the microprocessor interrupt input. The register
map is shown in
Table 11-1 .
8.1.1 Read-Write/Data Strobe Modes
The processor interface can operate in either read-write strobe mode or data strobe mode. When MODEC[1:0] =
00 the read-write strobe mode is enabled and a negative pulse on
RD performs a read cycle, and a negative pulse
on WR performs a write cycle. When MODEC[1:0] pins = 01 the data strobe mode is enabled and a negative pulse
on DS when RW is high performs a read cycle, and a negative pulse on DS when RW is low performs a write cycle.
The read-write strobe mode is commonly called the “Intel” mode, and the data strobe mode is commonly called the
“Motorola” mode.
8.1.2 Clear on Read
The latched status registers will clear on a read access. It is important to note that in a multi-task software
environment, the user should handle all status conditions of each register at the same time to avoid inadvertently
clearing status conditions. The latched status register bits are carefully designed so that an event occurrence
cannot collide with a user read access.
8.1.3 Interrupt and Pin Modes
The interrupt ( INT) pin is configurable to drive high or float when not active. The INTM bit controls the pin
configuration, when it is set the INT pin will drive high when not active. After reset, the INT pin is in high-impedance
mode until an interrupt source is active and enabled to drive the interrupt pin.