Cpu; Overview Of Cpu Features - Nintendo GAME BOY Programming Manual

Game Boy Programming Manual

2. CPU

2.1 Overview of CPU Features

The CPUs of DMG and CGB are ICs customized for DMG/CGB use, and have the following features.
CPU Features
Central to the 8-bit CPU are the following features, including an I/O port and timer.
! 127 x 8 bits of built-in RAM (working and stack)
! RAM for LCD Display: <DMG> 8 KB/<CGB>16 KB ( )
! Working RAM: <DMG> 8KB/<CGB> 32 KB
! Built-in 16-stage Frequency Divider
! Built-in 8-bit Timer
! 4 types of Internal Interrupts (maskable)
! 1 type of External Interrupt (maskable)
! Built-in DMA Controller
! Input Ports P10 ~ P13
! Output Ports P14 and P15
! Serial I/O Ports SIN, SCK, SOUT
! Infrared I/O Port <CGB only>
LCD Controller Functions
Game Boy is equipped with functions that provide control of the images displayed
on the LCD. Character data used for display is held in system RAM.
! DMG: 4 shades of gray; CGB: 32 shades of gray for each RGB color
! 160 x 144-dot liquid crystal display
! 8 x 8-dot composition of background and window characters
! 8 x 8 or 8 x 16-dot composition of OBJ characters
! Up to 40 objects displayable in 1 screen
! Up to 10 objects displayable on 1 horizontal line
! 40 x 32 bits of built-in RAM (OBJ-RAM for LCD)
! Control of 256 x 256-dot background
! Vertically and horizontally scrollable background
! Window-like functions
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