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06/19/2000

GL600USB/GL600USB-A/GL600USB-B

Revision 1.3

algorithm can detect any analog waveform from photo-sensor with amplitude larger than 1V. The ADC is a

high-speed converter. It takes less than 500ns to complete the conversion. Because GL600USB is running

at 3 MIPS for USB low speed application, only two dummy instructions should be added between write

PHSEL to read PHVAL.

4.5

GENERAL PURPOSE I/O PORTS

Interface with peripherals is conducted via up to 13 GPIO signals. These 13 signals are divided into two

ports: Port 1 and Port 2. Port 1 contains five lines (PORT1.0-PORT1.4) and Port 2 contains eight lines

(PORT2.0-PORT2.7). The Port 1 data register is located at data memory address 06h while the Port 2 data

register is located at data memory address 07h.

Port 2 is a low current port with analog input capability suitable for connecting photo-sensor. Port 1 is a

high current port capable of LED drive. Each GPIO line may include an internal pull-up or pull-down

resistor. Port 2’s internal pull-down resistor value can be programmed by option-code. Each output drive

has slew-rate control to reduce EMI. Please see the following table for details.

Driving capability

Pull-up resistor

Pull-down resistor

PORT1.0

20 mA

PORT1.1

20 mA

PORT1.2

4 mA

10K

Ω

PORT1.3

4 mA

10K

Ω

PORT1.4

4 mA

10K

Ω

PORT2.0

4 mA

4K

PORT2.1

4 mA

4K

Ω/8KΩ/16KΩ/32KΩ

PORT2.2

4 mA

4K

Ω/8KΩ/16KΩ/32KΩ

PORT2.3

4 mA

4K

Ω/8KΩ/16KΩ/32KΩ

PORT2.4

4 mA

4K

Ω/8KΩ/16KΩ/32KΩ

PORT2.5

4 mA

4K

Ω/8KΩ/16KΩ/32KΩ

PORT2.6

4 mA

4K

Ω/8KΩ/16KΩ/32KΩ

PORT2.7

4 mA

4K

Ω/8KΩ/16KΩ/32KΩ

Note 1: The pull-down resistor can be configured as 4K

Ω, 8KΩ, 16KΩ or 32KΩ by option-code.

Table 4 -3 General Purpose I/O Port Summary

4.6

TIMER INTERRUPT

The Timer Interrupt is generated when the TIMER register overflows from FFh to 00h. This overflow sets

bit TMROF (INTEN<2>). The interrupt can be masked by clearing bit TMROEN (INTEN<5>). Bit

TMROF must be cleared in software by the Timer module interrupt service routine otherwise the Timer

Interrupt will not be generated again. If prescaler is disabled, the timer register will increase every

instruction cycle. If prescaler is enabled, its increment cycle depends on PS0~PS2 bits in PSCON register.

4.7

USB ENGINE

The USB module contains three functional blocks: a 3.3-volt regulator, a low-speed USB transceiver, and

the Serial Interface Engine (SIE). The following details the function of the regulator, transceiver, and SIE.

4.7.1

Voltage Regulator

The USB data lines are required by the USB specification to have a maximum output voltage between 2.8V

and 3.6V. Because the GL600USB is a low speed USB device, the D- lines also are required to have an