6821.yaml

---
description: "Peripheral interface adapter"
aliases:     [68A21, 68B21]
package:     DIP
pincount:    40
family:      "Motorola"
datasheet:   "http://www.jameco.com/Jameco/Products/ProdDS/43596MOT.pdf"
pins:
  - num:  1
    sym:  GND
    desc: ground
  - num:  2
    sym:  PA0
    desc: port A
  - num:  3
    sym:  PA1
    desc: port A
  - num:  4
    sym:  PA2
    desc: port A
  - num:  5
    sym:  PA3
    desc: port A
  - num:  6
    sym:  PA4
    desc: port A
  - num:  7
    sym:  PA5
    desc: port A
  - num:  8
    sym:  PA6
    desc: port A
  - num:  9
    sym:  PA7
    desc: port A
  - num:  10
    sym:  PB0
    desc: port B
  - num:  11
    sym:  PB1
    desc: port B
  - num:  12
    sym:  PB2
    desc: port B
  - num:  13
    sym:  PB3
    desc: port B
  - num:  14
    sym:  PB4
    desc: port B
  - num:  15
    sym:  PB5
    desc: port B
  - num:  16
    sym:  PB6
    desc: port B
  - num:  17
    sym:  PB7
    desc: port B
  - num:  18
    sym:  CB1
    desc: peripheral control (port B)
  - num:  19
    sym:  CB2
    desc: peripheral control (port B)
  - num:  20
    sym:  Vcc
    desc: supply voltage
  - num:  21
    sym:  R/~W
    desc: read/write
  - num:  22
    sym:  CS0
    desc: chip select (active high)
  - num:  23
    sym:  ~CS2
    desc: chip select (active low)
  - num:  24
    sym:  CS1
    desc: chip select (active high)
  - num:  25
    sym:  E
    desc: clock
  - num:  26
    sym:  D7
    desc: data bus
  - num:  27
    sym:  D6
    desc: data bus
  - num:  28
    sym:  D5
    desc: data bus
  - num:  29
    sym:  D4
    desc: data bus
  - num:  30
    sym:  D3
    desc: data bus
  - num:  31
    sym:  D2
    desc: data bus
  - num:  32
    sym:  D1
    desc: data bus
  - num:  33
    sym:  D0
    desc: data bus
  - num:  34
    sym:  ~RESET
    desc: master reset (active low)
  - num:  35
    sym:  RS1
    desc: register select (address bus)
  - num:  36
    sym:  RS0
    desc: register select (address bus)
  - num:  37
    sym:  ~IRQB
    desc: interrupt output (active low)
  - num:  38
    sym:  ~IRQA
    desc: interrupt output (active low)
  - num:  39
    sym:  CA2
    desc: peripheral control (port A)
  - num:  40
    sym:  CA1
    desc: peripheral control (port A)
specs:
  - param: "Max. clock frequency"
    val:   [1 (6821), 1.5 (68A21), 2 (68B21)]
    unit:  MHz
  - param: "Pulse width, E low"
    val:   [430 (6821), 280 (68A21), 210 (68B21)]
    unit:  ns
  - param: "Pulse width, E high"
    val:   [450 (6821), 280 (68A21), 220 (68B21)]
    unit:  ns
  - param: "Min. ~RESET pulse length"
    val:   1
    unit:  "µs"
notes:
  - Port A is designed to drive CMOS logic to normal 30%/70% levels.
  - Port B uses three-state NMOS buffers and requires external resistors to pull up to CMOS levels.
  - Port B is capable of driving Darlingtons.
  - When in output mode, a read of Port A returns the actual pin states.
  - When in output mode, a read of Port B returns the contents of the output latch.
  - "RS=00, bit 2 of control register A=1: peripheral register A"
  - "RS=00, bit 2 of control register A=0: data direction register A"
  - "RS=01: control register A"
  - "RS=10, bit 2 of control register B=1: peripheral register B"
  - "RS=10, bit 2 of control register B=0: data direction register B"
  - "RS=11: control register B"
...