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HI-6121PCMF Datasheet(PDF) 7 Page - Holt Integrated Circuits |
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HI-6121PCMF Datasheet(HTML) 7 Page - Holt Integrated Circuits |
7 / 116 page The HI-6120 and HI-6121 have an internal address space of 32K 16-bit words. All memory addresses in this data sheet are expressed as hexadecimal numbers, using the C programming convention where the prefix “0x” denotes a hexadecimal value; e.g., 0x00FF represents 00FF hex. All device RAM and register address mapping is word oriented, rather than byte oriented. Register and memory addresses throughout this document reflect word addressing. For all HI-6121 and most HI-6120 applications, word oriented addressing applies. W When required by the application, the host bus interface HI-6120 is able to use byte transfers. To provide byte capability, the HI-6120 has a sixteenth bus address input, A0. Byte oriented addressing with the HI-6120 uses all 16 address pins, A15 to A0 to address 64K bytes. The A0 input denotes whether the first or second byte in the word is being addressed, while A15-A1 indicate the word address. This difference must be considered when assigning HI-6120 pointer values or accessing RAM or registers. From the microprocessor’s standpoint, any host-assigned RAM buffer address will be double the value of the buffer’s pointer stored in RAM. HI-6120 ONLY: This paragraph only applies to HI-6120 using 8-bit bus width. ord oriented addressing with the HI-6120 uses address inputs A15 to A1; address input A0 is not used as fifteen bits are sufficient for a 32K address range. All 8-bit microprocessors (and some 16-bit and 32-bit microprocessors) use (or can use) byte-oriented memory accesses. MEMORY AND REGISTER ADDRESSING Interrupt Log Clock Inputs Remote Terminal Address Inputs Integral Time-Tag Counter Dual Bus Transceivers Auto-Initialization Serial EEPROM Interface The device maintains information from the last 16 interrupts in a 32-word circular buffer in shared RAM known as the Interrupt Log. Two 16-bit words characterize each interrupt; one word identifies the interrupt type (Interrupt Identification Word) and one word identifies the command that generated the interrupt (Interrupt Address Word). After reset, the Interrupt Log Address Register is reset to the fixed starting address of the 32 word Interrupt Log. After each occurring interrupt, the device updates the register to point to the log address used for the next occurring interrupt. The 5-bit Remote Terminal address is set using pins RTA0 to RTA 4. The RTAP input pin should be set or reset to present matching odd parity. The state of the RT address and parity pins is latched into the Operational Status register upon rising edge on the master reset input. The state of the LOCK input is latched into the Operational Status register at the same time, and controls whether or not the active terminal address and parity in the Operational Status register can be overwritten by host writes into the register. Between Master Reset assertions, the state of the RTA and RTAP inputs is “don’t care”. If the value of RT address and parity in the Operational Status register has parity error, terminal operation is disallowed. The device has an automatic self-initialization feature. If self- initialization is enabled after master reset, the device reads configuration settings from external serial EEPROM to load the Descriptor Table, Illegalization Table, transmit mode command data and registers for terminal operation. Self-initialization can optionally initialize transmit data buffers with fixed data from EEPROM. A mechanism is provided to initially program or later modify the external serial EEPROM memory, by copying host-loaded tables and register values to the serial EEPROM. HARDWARE FEATURE SUMMARY A 50 MHz master clock input is required. The Time-Tag counter clock is selected from six internally generated frequencies, or may use an external clock input signal. A free-running 16-bit counter provides time-tag values that are recorded for each message transacted. The time-tag counter can be clocked from one of six internally generated frequencies, or from an external source. The user can enable automatic counter synchronization in response to “synchronize” mode commands, and optional host interrupts are provided for time-tag counter roll-over, and counter match to a stored value in the Time-Tag Utility register. Built-in bus transceivers provide direct interface between the device and MIL-STD-1553 bus isolation transformers. The transceivers convert digital data to and from differential Manchester II encoded bus signals. A pair of “transmit inhibit” input pins exercises direct control over transmission for both buses. The RT contains separate Manchester II encoders and decoders for each bus. Encoder-decoder logic interfaces directly with the dual-bus MIL-STD-1553 transceivers. The decoder checks for proper sync pulse and Manchester waveform, edge skew, correct number of bits and parity. During transmission, each encoded word is looped back through the decoder to check for errors. Bus sampling is clocked at 25 MHz, providing superior tolerance to zero- crossing distortion. MR MR Encoder and Decoders FUNCTIONAL OVERVIEW, Cont. HOLT INTEGRATED CIRCUITS 7 HI-6120, HI-6121 |
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