The BLINK gate array

Owned by Gunther Strube
Last updated: May 05, 2021 by Elpekos
6 min read

The Blink gate-array is a custom ASIC : NEC D65031GF168. This SMD is a uPD65000 series (low power 2 micron ASIC) with 138 rows of 24 columns, 3312 cells of 4 transistors.

GF stands for a flat packaging of 100 pins. 168 is the circuit type number identifying the blink design.

It contains the logic of :

  • the memory management unit (MMU)

  • the real time clock (RTC)

  • the Z80 clock and power management

  • the Z80 reset

  • the programmable interrupt controller (PIC)

  • the UART

  • the LCD controller

  • the EPROM programmmer

  • the speaker

The blink, this chip was product in 1987, week 14.

 

Pin Name Type Description 1 GND - Ground 2 VDD - +5V 3 IOR I Z80 /IORQ 4 CRD I Z80 /RD 5 MRQ I Z80 /MREQ 6 HLT I Z80 /HALT 7 NMIB O Z80 /NMI 8 INTB O Z80 /INT 9 CDB IO Z80 D1 10 ROUT O Z80 /RST 11 CDA IO Z80 D0 12 CM1 I Z80 /M1 13 CDH IO Z80 D7 14 CDC IO Z80 D2 15 CA0 O Z80 A0 16 CDG IO Z80 D6 17 CA1 O Z80 A1 18 CDF IO Z80 D5 19 CA2 O Z80 A2 20 CDD IO Z80 D3 21 CA3 O Z80 A3 22 CDE IO Z80 D4 23 CA4 O Z80 A4 24 CA5 O Z80 A5 25 CA15 O Z80 A15 26 CA6 O Z80 A6 27 CA14 O Z80 A14 28 GND - Ground 29 VDD - +5V 30 CA13 O Z80 A13 31 CA7 O Z80 A7 32 CA8 O Z80 A8 33 CA12 O Z80 A12 34 CA9 O Z80 A9 35 CA11 O Z80 A11 36 CA10 O Z80 A10 37 TxD O UART TXD 38 RTS O UART RTS 39 IRCE O RAM.0 /CE 40 GND - Ground 41 RxD I UART RXD 42 CTS I UART CTS 43 DCD I UART DCD 44 PM1 O Z80 clock (3.2768 MHz) 45 LP O LCD control, 10ms line pulse 46 FR O LCD control, 156us frame 47 XSCL O LCD control, 300ns data 48 LD0 O LCD data 49 LD1 O LCD data 50 LD2 O LCD data 51 LD3 O LCD data 52 VDD - +5V 53 GND - Ground 54 MA16 O Memory A16 55 MA15 O Memory A15 56 MA14 O Memory A14 57 MA12 O Memory A12 58 MA7 O Memory A7 59 MA13 O Memory A13 60 MA6 O Memory A6 61 MA8 O Memory A8 62 MA5 O Memory A5 63 WRB O Write enable /WE 64 MA9 O Memory A9 65 MA4 O Memory A4 66 MA11 O Memory A11 67 MA3 O Memory A3 68 IPCE O ROM.0 /CE 69 MA2 O Memory A2 70 MA10 O Memory A10 71 MA1 O Memory A1 72 MA0 O Memory A0 73 MDH IO Memory D7 74 MDA IO Memory D0 75 MDG IO Memory D6 76 MDB IO Memory D1 77 MDF IO Memory D5 78 MDC IO Memory D2 79 VDD - +5V 80 GND - Ground 81 MDE IO Memory D4 82 MDD IO Memory D3 83 MA17 O Memory A17 84 MA18 O Memory A18 85 MAW O Memory A19 86 SE1 O Slot1 /CE 87 POE O PSRAM /OE (refreshed) 88 ROE O ROM /OE 89 PGMB O Slot 3 /WE (Program Byte) 90 EOE O Slot 3 /OE (Eprom OE) 91 SE3 O Slot 3 /CE 92 FLP I Flap 93 SE2 O Slot2 /CE 94 SNS I Sens line (card insertion) 95 VPON O VPP on 96 BTL I Batt low 97 RIN I Reset input 98 MCK I Master clock (9.8304 MHz) 99 SCK I Standby clock (25.6 KHz) 100 SPKR O speaker

 

The original notes as supplied to Cambridge Computer were lost during the time of the company's move from Cambridge to Scotland. The following notes comes from the patent WO88/09007 (Richard MILLER and James WESTWOOD) and WO88/09573 (James WESTWOOD).

SNS

Card insertion or removal is detected by SNS. The card module slot connector is made such that during insertion or removal the SNS is shorted to ground. When SNS goes low, an NMI is fired and initiate a shutdown. This prevent any loss off data or system crash.

POE, ROE, EOE, pseudo-static RAM refresh

  • POE : Pseudo-static OE

  • ROE : Rom OE

  • EOE : Eprom OE

When Z80 is running and LCD is on, the refresh is performed by the LCD controller reading the memory.

When LCD is off (DOZE state), the 42832 is not in standby mode, it needs to be refreshed.
POE provides this refresh, ROE does not. POE is tracked to slot 0 RAM, slot 1 and slot 2 connectors.

Pseudo static RAM card are not supported in slot 3. The POE line in slot 3 connector is replaced by the EOE. EOE is driven by the EPR register.

Z80 Refresh signal is not wired. Refresh logic in blink is done from CRD, CM1, MRQ (negative signals) :

POE = ROE | ( CRD & ~CM1 & ~MRQ)

Clocks and power management

Z80 clock (PM1) is driven by the Blink, the CMOS Z80 can be stopped without losing register state.

Active : PM1 = MCK / 3 = 9.8304 / 3 = 3.2768MHz

Snooze : PM1 is stopped

Coma : PM1 = SCK = 25.6KHz

Doze : PM1 is stopped during some eprom programming phase (see below)

Master clock is 9.83MHz for the LCD controller reading screen files in memory.

It will be appreciated that the CPU clock must be stopped and started at appropriate points in the clock cycle. In practice it may be stopped halfway through a cycle and restarted at the beginning of another cycle.

LCD controller

A 640 bits shift register is used to build the current line and shift nibbles to the LCD data lines.

The LCD frame rate is 100Hz, one page every 10ms (LP).

One line is sent every 156.25us (FR). A burst of 160 nibbles at 3.2768 MHz (300ns period) are sent. It last 48us and is followed by a 108.25us inactive period.

 

Slot 3 and Eprom programming

The connector for the top slot, slot 3, is moreover equipped to apply a programming voltage Vpp to enable an EPROM module to be programmed. By means of the present invention it is possible to effect this programming directly off the address and data buses extended to the module via the gate array and connector. Slot 3 normally operates like slots 1 and 2, i.e. normal read and (if RAM is in the slot) write operations may be effected. However a bit is used in the logic array as a flag to select (OVERP in COM register) between normal operation and programming mode. When this bit is set, the circuit described below with-reference to Fig. 2 is brought into action. A separate bit is set/reset to control the application of the programming voltage Vpp (VPP in COM register).

Features of the logic array are shown in Fig. 2. A particular address range, namely the top slot, is dedicated to EPROM programming, when the flag bit mentioned above is set. When the
CPU wishes to program an EPROM byte, it establishes the required address by way of the bus A0 to A15 and one of the registers 15 (B0 to B7) and the required data is put on to the data bus D0 to D7.

 

The logic array includes a decoder 22 which detects any extended write address in the programming range (B6 = B7 = 1) and issues a signal PROGRAMA which stops the CPU clock PHI CPU, via a latch 26 and gate 28. After a delay, introduced by delay stage 23, of about 2 seconds (FRONT PORCH) a latch 27 is set, which in turn will activate the appropriate control signals to the EPROM (such as PGM, OE and CE, depending on the EPROM type). Delay duration and state of PGM, EOE, SE3 are set in EPR register.

The delay stage 24, is programmable, to accept various EPROM programming times After the delay 24, the latch 27 is reset, thus releasing the EPROM from its programming mode. A delay 25 (BACK PORCH) lasts for about 2 seconds, after which the clock to the CPU is started again. Vpp is applied throughout this sequence of operations. The delay time of the delay 24 may be programmed to allow the CPU to perform a program then verify cycle repeatedly in a training stage during which the appropriate minimum delay for secure programming of the EPROM is ascertained.

It can thus be seen that the EPROM is programmed directly off the address and data buses A, D'0 - D'7 rather than off a separate register set up to buffer the input signals which have to be held over a very large number of CPU clock cycles.

 

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