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**82C281/282 Cache Sx/AT (386SX) <08/22/91
***Notes:...
***Info:
The 82C281/2 is a highly integrated AT system logic VLSI for high end
386 Sx AT systems. It integrates the logic for local DRAM control, AT
bus control, cache memory control, and data bus control and is
designed for systems running at 16MHz, 20MHz, and 25MHz.
A high performance, compact 386 Sx/AT system can be implemented easily
with 82C281/2 and standard peripheral controllers like the 82C206 or
the VLSI 82C100 plus Dallas Semiconductor DS1287.
2 System Operation
The following sections describe the detailed system operations of the
82C281 /2 based Sx-AT design.
2.1 Reset
The power good (PWRGD) signal from power supply drives the system into
the initial state when it is asserted low. The 82C281/2 forces CPURST,
SYSRST, and NPRST high as soon as PWRGD becomes inactive. When the
PWRGD is high, the chip deactivates the CPURST, SYSRST, and NPRST
after 128 CLK2 cycles.
2.2 Cache Interface
The 82028112 cache control unit monitors the HIT# pin and the internal
NCA# signals to determine if it is a cache hit or cache miss
cycle. During the cache read miss cycle, the cache controller asserts
TAGWE# to update the TAG RAM, CAWE# is also asserted to update the
cache data memory.
The A1 CNT output will be forced high then low to toggle CPU address
bit 1 to cache data memory to achieve the prefetch.
During cache write hit cycles, the cache controller asserts the CAWE#
signal to update the cache data memory.
2.3 Local DRAM Interfaces
Local DRAM is located on the CPU local data bus and is buffered by a
F244 and F373 buffer. During CPU read cycles data is routed from main
memory to CPU through F244’s Which are controled by LMRD#. During CPU
write cycles, data is latched by F373 latches with the PDLTH signal
from the 82C281/2 while DWE# controls the transceivers' enable. The
main memory subsystem asserts the LMRD# while CPU, DMA, and external
master card reads the local DRAM. DWE# is asserted during local DRAM
memory write.
For local memory read cycles, the memory controller reads two bytes at
a time. The read data passes into 82C281/2 where the parity checking
function is executed.
For the local memory write cycles, the data bus control unit generates
the parity bits to be stored into the local DRAM.
2.4 System BIOS ROM
If the system BIOS ROM is not shadowed, the ROM cycles are treated as
AT cycles. The system designer can put the ROM on the XD bus as an
8-bit slave or SD bus as a 16-Bit slave.
For a 16-bit slave, ROMCS# is connected to M16# through an open
collector driver such as a 7407, the 82C281/2 monitors M16# to
determine the width of the ROM data path.
2.5 I/O Ports located on the XD bus
For l/O ports located on the XD bus, the XDIR# is activated. I/O ports
0F0H - 0FFH are reserved for the coprocessor.
2.6 Refresh Cycles
The AT bus control unit arbitrates the hold request from 82C206 and
the refresh request from 82C281/2 internal, then decides which is the
next owner of the bus once the CPU relinquishes it. The refresh
request generated internally by 82C281/2 can be programmed as every
15.9 micro-seconds or every 95.5 micro-seconds for slow refresh
DRAM. lf the bus is granted for refresh cycles, the AT bus control
unit asserts RFSH# and MEMRD# commands and also generates the refresh
address.
2.7 DMA Cycles
The hold request from the 82C206 initiates DMA/Master transfers. The
82C281/2 performs the arbitration between HRQ and refresh
request. After the CPU acknowledges by asserting HLDA, and DMA request
wins the arbitration, the 82C281/2 sends HLDA1 to the 82C206
acknowledging the request. The 820206 then asserts DMA16# and
activates ADS16# to start 16-bit DMA transfers, or asserts DMA8# and
activates ADS8# to start 8-bit DMA transfers.
***Configurations:...
***Features:...
**82C283 386SX System Controller c:91...
**82C291 SXWB PC/AT Chipset (386SX) c:91...
**82C295 SLCWB PC/AT Chipset (386SX) ?...
**82C381/382 HiD/386 (386DX) c:89...
**82C391/392 386WB PC/AT Chipset (386DX) <Dec90...
**82C461/462 Notebook PC/AT chipset [no datasheet] ?...
**82c463 SCNB Single Ship Notebook c:92...
**82c465MV/A/B Single-Chip Mixed Voltage Notebook Solution <Oct97...
**82C481?/482? HiP/486 & HiB/486 [no datasheet] Oct89...
**82C491/392 486WB PC/AT Chipset <04/21/91...
**82C493/392 486SXWB <10/21/91...
**82C495SX/392SX LCWB PC/AT chipset [no datasheet] ?...
**82C495SLC DXSLC 386/486 Low Cost Write Back c:92...
**82C495XLC PC/AT Chip Set c:93...
**82c496A/B DXBB PC/AT Chipset <Mar92...
**82C496/7 DXBB PC/AT Chipset (Cached) <01/16/92...
**82C498 DXWB PC/AT chipset [no datasheet] ?...
**82C499 DXSC DX System Controller c:93...
**82C546/547 Python PTM3V c:94...
**82C556/7/8 Viper [no datasheet] ?...
**82C556/7/8N Viper-N Viper Notebook Chipset <05/25/95...
**82C556M/7M/8E Viper-N+ Viper Notebook Chipset c:96...
**82C566/7/8 Viper-Max Chipset Scalable MultiMedia PC Solution ?...
**82C571/572 486/Pentium c:93...
**82C576/7/8 Viper Xpress [no datasheet] ?...
**82C576/8/9 Viper XPress+ [no datasheet, some info] <01/16/97...
**82C596/597 PTMAWB Pentium Adaptive Write-back (Cobra) c:93...
**82C650/1/2 Discovery (Pentium Pro) [no datasheet] ?...
**82C681/2/6/7 386/486WB EISA c:92...
**82C683 386/486AWB EISA [no datasheet] ?...
**82C693/6/7 Pentium uP Write Back Cache EISA c:93...
**82C700 FireStar c:97...
**82C701 FireStar Plus c:97...
**82C750 Vendetta [no datasheet] ?...
**82c801 SCWB2 DX Single Chip Solution c:92...
**82C802 SCWB2 PC/AT Single Chip [no datasheet] ?...
**82C802G/GP System/Power Management Controller (cached) c:93...
**82C895 System/Power Management Controller (cached) c:Sep94...
**82C898 System/Power Management Controller (non-cache)c:Nov94...
**
**Support Chips:
**82C601/2 Buffer Devices <Nov94...
**82C822 PCIB (VLB-to-PCI bridge) c:94...
**Other:...
*PC CHIPS/Amptron/Atrend/ECS/Elpina/etc...
*SIS...
*Symphony...
*TI (Texas Instruments)...
*UMC...
**UM82C*** (IBM/INTEL Direct replacement) c87
Note: Dates vary for when these chips were first available. Two
databooks have been used one from '86 the other from '91. Not all the
chips are listed in the '86 databook, the date of '87 is an
assumption.
PC/XT:
IBM: UMC: Desc:
Intel 8284 UM82C84A 25MHz CMOS Clock Generator and Driver
Intel 8288 UM82C88 Bus Controller
Intel 8259 UM8259A Programmable Interrupt Controller also UM82C59A-2 (CMOS version)
Intel 8237 UM8237A 3-5MHz Programmable DMA Controller (DMAC)
Intel 8253 UM8253*2 2.6-5MHz Programmable Interval Timer
Intel 8255 UM82C55A* Programmable Peripheral Interface
Note: * indicates: possible compatibility, datasheet does not state
explicitly. YMMV.
Note: *2 indicates: The UM8253 can be replaced with the
UM82C54/-2. The datasheet says it is a superset of the 8253, and
works up to 10MHz. Also it's compatible with the 8254. AT: IBM:
UMC: Desc: Intel 82284 UM82C284* 10-12.5MHz Clock Generator and
Ready Interface Intel 82288 UM82C288* 10-12.5MHz Bus Controller
Intel 8254 UM82C54/-2 8-10MHz CMOS Programmable Interval Timer
Intel 8259 UM8259A Programmable Interrupt Controller also
UM82C59A-2 (CMOS version) Intel 8237 UM8237A 3-5MHz Programmable
DMA Controller (DMAC) 74LS612 UM74HCT612* Memory Mapper MC146818
RTC UM82C6818* Real-Time Clock (RTC) Intel 8047 ?? Keyboard
Controller
Note: * indicates: possible compatibility, datasheet does not state
explicitly. YMMV.
**UM82C088 PC/XT Integration Chip <91...
**UM82C230 286AT MORTAR Chip Set <91...
**UM82C210 386SX/286 AT Chip Set <91...
**UM82C3xx Twinstar & UM82C336F/N & UM82C39x [no datasheet] ?...
**UM82C380 386 HEAT PC/AT Chip Set <91...
**UM82C480 386/486 PC Chip Set c91
***Info:...
***Configurations:...
***Features:...
**UM82C493/491 ??????????????? [no datasheet] ?...
**UM8498/8496 486 VL Chipset "Super Energy Star Green"[no dsheet]c94...
**UM8881/8886 HB4 PCI Chipset "Super Energy Star Green"[no dsheet]c94...
**UM8890 Pentium chipset [no datasheet] ?...
**
**Support Chips:
**UM82152 Cache Controller (AUStek A38152 clone) <91...
**UM82C852 Multi I/O For XT <91...
**UM82C206 Integrated Peripheral Controller <91
***Info:...
***Versions:...
***Features:...
**UM82c45x Serial/Parallel chips ?...
**Other chips:...
*Unresearched:...
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