Maxim DS33Z41 specifications Processor Interface, Read-Write/Data Strobe Modes, Clear on Read

DS33Z41 Quad IMUX Ethernet Mapper

8.1Processor Interface

Microprocessor control of the DS33Z41 is accomplished through the 20 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 11-11 and Figure 11-12. When MODEC[1:0] = 01, bus timing is in Motorola mode, as shown in Figure 11-13 and Figure 11-14. The address space is mapped through the use of 8 address lines, A0 - A7. Multiplexed Mode is not supported on the processor interface.

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 (RW) 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 9-1.

8.1.1Read-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.

8.1.2Clear 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.

8.1.3Interrupt 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.

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