Revision 1.6
-9-
02/28/2000
4. FUNCTIONAL DESCRIPTION
The Genesys Logic GL602USB micro-controller is optimized for PC keyboard. This USB microcontroller
conforms to the low-speed (1.5Mbps) requirements of the USB Specification version 1.1. The micro-controller is a
self-contained unit with an USB SIE, an USB transceiver, an 8-bit RISC-like microcontroller, a timer, data and
program memories. It supports one USB device address and four endpoints (include endpoint 0).
4.1 MEMORY ORGANIZATION
The memory in the microcontroller is organized into user program memory in program ROM and data memory
in SRAM space.
4.1.1 Program Memory Organization
The 12-bit Program Counter (PC) is capable of addressing 4K x 14 of program space. All of the 4K * 14 ROM
space can be used. The program memory space is divided into two functional groups: Interrupt Vectors and
program code. After a reset, the Program Counter points to location zero of the program space and all registers
are reset to the default value. After a timer interrupt, the Program Counter points the location 0x0004 of the
program space.
Address
After Reset
→
0x0000
Reset Vector
After Timer Interrupt
→
0x0004
Timer Interrupt Vector
0x0005
0x0FFF
4K x 14 ROM
Figure 4-1 Program Memory Space
4.1.2 Data Memory Organization
The data memory is partitioned into two Banks that contain the General Purpose Registers, MCU Function
Registers and USB Function Registers. Bit BS is the bank select bit.
BS (STATUS<5>) = 1
→ Bank 1
BS (STATUS<5>) = 0
→ Bank 0
The lower locations of each Bank are reserved for MCU Function Registers and USB Function Registers.
Above the MCU Function Registers and USB Function Registers are General Purpose Registers implemented
as SRAM. Both Bank 0 and Bank 1 contain MCU Function Registers. USB Function Registers are located in
Bank 0. Some “high use” MCU Function Registers from Bank 0 are mirrored in Bank 1 for code reduction and
quicker access.
Data
Memory
Address
Data Memory
Address
00h
INDR
80h
INDR
01h
TIMER
81h
PSCON
02h
PCL
82h
PCL
03h
STATUS
83h
STATUS
04h
INDAR
84h
INDAR
05h
85h
06h
PORT1
86h
PORT1CON
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