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MU9C4485L-12TCC Datasheet(PDF) 10 Page - MUSIC Semiconductors |
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MU9C4485L-12TCC Datasheet(HTML) 10 Page - MUSIC Semiconductors |
10 / 28 page WidePort LANCAM® Family Rev. 2 10 OPERATIONAL CHARACTERISTICS Continued in Enhanced mode, it is not necessary to unlock the daisy chain with a NOP instruction before command or data writes after a non-matching compare, as required in Standard mode. Segment Control Register (SC) The Segment Control register, as shown in Table 10, is accessed using a TCO SC instruction with the register contents placed on DQ15–0. On read cycles, DQ31–16 will be the upper 16 bits of the Status register, and D15, D10, D5, and D2 always read back as 0s. Reserved locations D14, D12, D9, D7, D4, and D1 should always be set to 0 and as such will also read back as 0s. Either the Foreground or Background Segment Control register will be active, depending on which register set has been selected, and only the active Segment Control register will be written to or read from. The Segment Control register contains dual independent incrementing counters with limits, one for data reads and one for data writes. These counters control which 32-bit segment of the 64-bit internal resource is accessed during a particular data cycle on the 32-bit data bus. The actual destination for data writes and source for data reads (called the persistent destination and source) are set independently with SPD and SPS instructions, respectively. Each of the two counters consists of a start limit, an end limit, and the current segment pointer, each a single bit representing either the lower segment (0) or the upper segment (1). The current segment pointer can be set to either 0 or 1 even if that value is outside the range set by the start and end segments. The counters count up from the current segment pointer to the end limit and then roll over back to the start limit. If a sequence of data writes or reads is interrupted, the Segment Control register can be reset to its initial start limit values with the RSC instruction. After a reset, both Source and Destination counters are set to count from Segment 0 to Segment 1 with an initial value of 0. Page Address Register (PA) The Page Address register is loaded using a TCO PA instruction on DQ31–16 with a user selected 16-bit value (not FFFFH) on DQ15–0. During reads of the PA register, DQ31–16 will all be 0. The entry in the PA register is used to give a unique address to the different devices in a daisy chain. In a daisy chain, the PA value of each device is loaded using the SFF instruction to advance to the next device, as shown in the “Setting Page Address Register Values” section. A software reset (using the Control register) does not affect the Page Address register. Device Select Register (DS) The Device Select register is used to select a specific (target) device using the TCO DS instruction in DQ31–16 and setting the 16-bit DS value in DQ15–0 equal to the target’s PA value. The DS register can be read through DQ15–0 with DQ31–16 returning the upper 16 bits of the Status register. In a daisy chain, setting DS = FFFFH will select all devices. However, in this case, the ability to read information out of the device is restricted as shown in Tables 6a and 6b. A software reset (using the Control register) does not affect the Device Select register. Address Register (AR) The Address register points to the CAM memory location to be operated upon when a M@[AR] or M@aaaH is part of the instruction. It can be loaded directly by using a TCO AR instruction or indirectly by using an instruction requiring an absolute address, such as MOV aaaH, CR,V. The AR register can be read through DQ15–0 with DQ31–16 returning the upper 16 bits of the Status register. After being loaded, the Address register value will then be used for the next memory access referencing the Address register. A reset sets the Address register to zero. Control Register bits CT3 and CT2 set the address to automatically increment or decrement (or not change) during sequences of Command or Data cycles. The Address register will change after executing an introduction that includes M@[AR] or M@aaaH, or after a data access to the end limit segment (as set in the Segment Control register) when the persistent source or destination is M@[AR] or M@aaaH. Either the Foreground or Background Address register will be active, depending on which register set has been selected, and only the active Address register will be written to or read from. Next Free Address Register (NF) The WidePort LANCAM automatically stores the address of the first empty memory location in the Next Free Address register, which is then used as a memory address pointer for M@NF operations. The Next Free Address register, shown in Table 11, can be read through DQ15–0 using a TCO NF instruction. DQ31–16 will return the upper 16 bits of the Status register. By taking /EC LOW during the TCO NF instruction cycle, only the device with /FI LOW and /FF HIGH will output the contents of its Next Free Address register, which gives the Next Free address in a system of daisy-chained devices. The Next Free address may be read from a specific device in the chain by setting the Device |
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