Using Devices - Jimmer1/Chip16 GitHub Wiki

As explained in the Chip16 Architecture, Devices are addons that extend the functionality of the Chip16 system. By implementing an interface using only 4 instructions, Devices can do a variety of exotic things that aren't necessarily possibly in a default Chip16 system.

These 4 instructions are as follows:

Mnemonic - Opcode - Description

  • WRB - DXNN - Writes a number of bytes specified by the 8-bit constant NN from the memory pointed to by M to Device X.
  • RDB - FXNN - Reads a number of bytes from Device X, specified by the 8-bit constant NN, to the memory pointed to by M.
  • DPS - EX00 - Sets the 16-bit pointer of Device X to the value held in register 14.
  • DPG - EX01 - Sets r14 to the value of the pointer of Device X.

DPS and DPG have the same effect on all Devices which is to set and get the 16-bit internal pointer.

What happens when a number of bytes are written to a Device is Device specific. I shall outline the effects of each instruction on each of the 3 standard Devices below:

  • ConsoleIO - 16-bit internal pointer is a format code with 0 representing ASCII and 1 representing hexadecimal.

    • WRB - Prints N bytes to the console in the format of the format code.
    • RDB - Reads N bytes from the console in the format of the format code.

  • MemoryDevice - 16-bit internal pointer holds the address of memory from which you read bytes and to which you write them.

    • WRB - Writes N bytes to the Device memory pointed to by the 16-bit internal pointer.
    • RDB - Reads N bytes from the Device memory pointed to by the 16-bit internal pointer.

  • RomDevice - 16-bit internal pointer functions the same as the MemoryDevice's pointer.

    • WRB - Does nothing.
    • RDB - Works the same as the RDB instruction of the MemoryDevice.

I shall use the ConsoleIO Device to demonstrate how these instructions are used, the interface is the same across Devices.

Recall: By default, the ConsoleIO Device is in port 0.

WRB

code = [
    0x60, 0x00, # acr r0, 0 # r0 = 0
    0x60, 0x00, # acr r0, 0 # r0 = 0
    0xA0, 0x00, # smp 0     # M = 0
    0xD0, 0x04  # wrb d0, 4 # write(d0, 4)
]

RDB

code = [
    0xA0, 0x00, # smp $     # M = 4
    0xF0, 0x04, # rdb d0, 4 # read(d0, 4)
]

DPS

code = [
    0x6F, 0x01, # acr r15, 0x01 # r15 = 1
    0xE0, 0x00, # dps d0        # d0.P = r15
]

DPG

code = [
    0xE0, 0x01 # dpg d0 # r15 = d0.P
]

Next: Terminating A Program