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LAN9211 数据表(PDF) 36 Page - SMSC Corporation |
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LAN9211 数据表(HTML) 36 Page - SMSC Corporation |
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36 / 147 page ![]() High-Performance Small Form Factor Single-Chip Ethernet Controller with HP Auto-MDIX Support Datasheet Revision 2.9 (03-01-12) 36 SMSC LAN9211 DATASHEET 3.8 General Purpose Timer (GP Timer) The General Purpose Timer is a programmable block that can be used to generate periodic host interrupts. The resolution of this timer is 100uS. The GP Timer loads the GPT_CNT Register with the value in the GPT_LOAD field and begins counting down when the TIMER_EN bit is set to a ‘1.’ On a reset, or when the TIMER_EN bit changes from set ‘1’ to cleared ‘0,’ the GPT_LOAD field is initialized to FFFFh. The GPT_CNT register is also initialized to FFFFh on a reset. Software can write the pre-load value into the GPT_LOAD field at any time; e.g., before or after the TIMER_EN bit is asserted. The GPT Enable bit TIMER_EN is located in the GPT_CFG register. Once enabled, the GPT counts down either until it reaches 0000h or until a new pre-load value is written to the GPT_LOAD field. At 0000h, the counter wraps around to FFFFh, asserts the GPT interrupt status bit and the IRQ signal if the GPT_INT_EN bit is set, and continues counting. The GPT interrupt status bit is in the INT_STS Register. The GPT_INT hardware interrupt can only be set if the GPT_INT_EN bit is set. GPT_INT is a sticky bit (R/WC); i.e., once the GPT_INT bit is set, it can only be cleared by writing a ‘1’ to the bit. Table 3.8 Endian Ordering Logic Operation FIFO Access via Data FIFO Port (00h-3Ch) Direct FIFO Access via FIFO_SEL CSR Access Host Data Bus Host Data Bus Host Data Bus D[15:8] D[7:0] D[15:8] D[7:0] D[15:8] D[7:0] FPORTEND=0 FSELEND=0 A1=1 3 2 323 2 A1=0 1 0 101 0 FPORTEND=1 FSELEND=0 A1=1 0 1 323 2 A1=0 2 3 101 0 FPORTEND=0 FSELEND=1 A1=1 32 0 13 2 A1=0 10 2 31 0 FPORTEND=1 FSELEND=1 A1=1 0 1 0 13 2 A1=0 2 3 2 31 0 FPORTEND=0 FSELEND=0 A1=1 1 0 101 0 A1=0 3 2 323 2 FPORTEND=1 FSELEND=0 A1=1 2 3 101 0 A1=0 0 1 323 2 PORTEND=0 FSELEND=1 A1=1 10 2 31 0 A1=0 32 0 13 2 PORTEND=1 FSELEND=1 A1=1 2 3 2 31 0 A1=0 0 1 0 13 2 |
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