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Multiface: Difference between revisions
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==== Technical details ==== | ==== Technical details ==== | ||
We haven't got a perfect schematic of Multiface 128. There is a [ | We haven't got a perfect schematic of Multiface 128. There is a [https://www.worldofspectrum.org/pub/sinclair/technical-docs/Multiface128_Schematics.zip PCB layout] and a [https://www.worldofspectrum.org/pub/sinclair/hardware-info/Multiface128_Manual.pdf manual] on WOS. | ||
The interface is build up 10 [http://en.wikipedia.org/wiki/7400_series 74LS] [http://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logic TTL] ICs, a [[2764 EPROM|2764]] 8K EPROM and a [[6264 SRAM|6264]] 8K [http://en.wikipedia.org/wiki/Static_random-access_memory static RAM]. There are 4 D flip-flop (2x74LS74 IC4 and IC7) to manage RED BUTTON/NMI, stealth mode and store video memory page. | The interface is build up 10 [http://en.wikipedia.org/wiki/7400_series 74LS] [http://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logic TTL] ICs, a [[2764 EPROM|2764]] 8K EPROM and a [[6264 SRAM|6264]] 8K [http://en.wikipedia.org/wiki/Static_random-access_memory static RAM]. There are 4 D flip-flop (2x74LS74 IC4 and IC7) to manage RED BUTTON/NMI, stealth mode and store video memory page. | ||
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we can found an error and several questionable things. | we can found an error and several questionable things. | ||
* A, (questionable) Stealth mode flip-flop (IC7) data input pin (2) not connected. It should be connected to +5V, e.g. to the adjacent 72LS32 (IC6) Vcc pin (14). | * A, (questionable) Stealth mode flip-flop (IC7) data input pin (2) not connected. It should be connected to +5V, e.g. to the adjacent 72LS32 (IC6) Vcc pin (14). | ||
* B, (error) The circled track (horizontal red) is connect IC3 2nd (based on Texas Instruments [ | * B, (error) The circled track (horizontal red) is connect IC3 2nd (based on Texas Instruments [https://www.ti.com/lit/ds/symlink/sn74ls27.pdf 74LS27 datasheet]) gate's output (pin 9) with IC9 1st (based on [https://www.ti.com/lit/ds/symlink/sn74ls32.pdf 74LS32 datasheet]) gate's output (pin 3). This track could not be here. | ||
* C, (questionable) Unused via. | * C, (questionable) Unused via. | ||
* D. (questionable) Unused via pair. | * D. (questionable) Unused via pair. | ||
* E, (questionable) IC9 1st (based on Texas Instruments [ | * E, (questionable) IC9 1st (based on Texas Instruments [https://www.ti.com/lit/ds/symlink/sn74ls32.pdf 74LS32 datasheet]) gate's 1st input pin (1) is unconnected. It should be connected somewhere probably the nearby {{overline|WR}} track (via of 6264 SRAM's pin (26) above this pin). So this gate makes a {{overline|WR}} + A15 logical function. | ||
* F, (questionable) IC9 3rd (based on Texas Instruments [ | * F, (questionable) IC9 3rd (based on Texas Instruments [https://www.ti.com/lit/ds/symlink/sn74ls32.pdf 74LS32 datasheet]) gate output (pin 8) not connected somewhere. The track ended with a lone via. | ||
There are three address decoding logic: | There are three address decoding logic: | ||
* IC1 ([https://www.futurlec.com/Datasheet/74ls/74LS260.pdf 74LS260] 2x 5-input NOR gates), IC2 ([https://www.ti.com/lit/ds/symlink/sn74ls30.pdf 74LS30] a 8 input-NAND gate), one gate (2nd) of IC3 ([https://www.ti.com/lit/ds/symlink/sn74ls27.pdf 74LS27] 3x 3-input NOR gates) and one gate (2nd) of IC9 ([https://www.ti.com/lit/ds/symlink/sn74ls32.pdf 74LS32] 4x 2-input OR gates) decode opcode fetch from #0066 or #0067 (A1-A15, {{overline|M1}}, {{overline|MERQ}} and {{overline|RD}}). This used to trigger the Multiface 8k ROM (and of course of 8k RAM) to page in after the RED BUTTON push initiates an [[Non Maskable Interrupt]] (pulls {{overline|NMI}} line). | * IC1 ([https://www.futurlec.com/Datasheet/74ls/74LS260.pdf 74LS260] 2x 5-input NOR gates), IC2 ([https://www.ti.com/lit/ds/symlink/sn74ls30.pdf 74LS30] a 8 input-NAND gate), one gate (2nd) of IC3 ([https://www.ti.com/lit/ds/symlink/sn74ls27.pdf 74LS27] 3x 3-input NOR gates) and one gate (2nd) of IC9 ([https://www.ti.com/lit/ds/symlink/sn74ls32.pdf 74LS32] 4x 2-input OR gates) decode opcode fetch from #0066 or #0067 (A1-A15, {{overline|M1}}, {{overline|MERQ}} and {{overline|RD}}). This used to trigger the Multiface 8k ROM (and of course of 8k RAM) to page in after the RED BUTTON push initiates an [[Non Maskable Interrupt]] (pulls {{overline|NMI}} line). | ||
* One gate (1st) of IC3, one gate (1st) of IC5 and one gate (1st) of IC10 ([ | * One gate (1st) of IC3, one gate (1st) of IC5 and one gate (1st) of IC10 ([https://www.ti.com/lit/ds/symlink/sn74ls00.pdf 74LS00] 4x 2-input NAND gates) and two gate (2nd and 4th) of IC6 ([https://www.ti.com/lit/ds/symlink/sn74ls32.pdf 74LS32] 4x 2-input-OR gate) decode port I/O from/to '''xxxx xxxx x011 x1xx''' address (A2, A4-A5, {{overline|IORQ}}, {{overline|RD}} and {{overline|WR}}).The aid of a gate (3) of IC6 and 2 gates (3rd and 4th) of IC5 (A7) it used to manage the RED BUTTON stealth and page in/out logic. | ||
* One gate (1st) of IC9 and one gate (2nd) of IC3 decode write to I/O port '''0xxx xxxx xxxx xx0x''' (A1, A15 and {{overline|WR}}). This used to store (D3) the selected video page in the 2nd D flip-flop of IC7 ([https://www.ti.com/lit/ds/symlink/sn74ls74a.pdf 74LS74] 2x D-type flip-flop). See: [[ZX Spectrum 128#Paging|ZX Spectrum 128 Paging]] | * One gate (1st) of IC9 and one gate (2nd) of IC3 decode write to I/O port '''0xxx xxxx xxxx xx0x''' (A1, A15 and {{overline|WR}}). This used to store (D3) the selected video page in the 2nd D flip-flop of IC7 ([https://www.ti.com/lit/ds/symlink/sn74ls74a.pdf 74LS74] 2x D-type flip-flop). See: [[ZX Spectrum 128#Paging|ZX Spectrum 128 Paging]] | ||