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ST2204 Scheda tecnica(PDF) 8 Page - Sitronix Technology Co., Ltd. |
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ST2204 Scheda tecnica(HTML) 8 Page - Sitronix Technology Co., Ltd. |
8 / 24 page ST2204 Ver 0.6 8/24 2008/11/10 7 7.. G GP PIIO O The ST2204 consists of 48 general-purpose I/O (GPIO) which are divided into six I/O ports: Port-A/B/C/D/E and Port-L. Each single pin can be programmed to be input or output. This is controlled by port direction control registers PCx. Setting bit of PCx makes respective pin to output, and clearing this bit for input. There are two options: pull-up/down for inputs of Port-C but only pull-up for inputs of the other ports. In case of output, there are open-drain/CMOS options for outputs of PortC but only CMOS for the other ports. Refer to TABLE 7-1. TABLE 7-1 I/O Types Of GPIO Ports I/O Types I/O Mode Port-A/B/D/E/L Port-C Input Pull-up/Pure Pull-up/Pull-down/Pure Output CMOS Open-drain/CMOS Input Mode In case of input function, port data registers Px reflect the values on associated pins. Besides read instruction for data of signals input, writing to register Px selects I/O types of pins, pull-up or pull-down. Setting bits of all port data register Px to select pull-up type. Clearing bits of only PC to select pull-down type for pins of Port-C. There are no pull-down resistors for Port-A/B/D/E and Port-L, thereby no pull-down resistors will be enabled if clearing bits of PA, PB, PD, PE and PL. Pull-up resistors of Port-A/B/D/E/L are also controlled by PULL bit (bit7 of port miscellaneous register PMCR), “0” is to disable, while “1” is to enable them. The pull-up/pull-down resistors of Port-C are further controlled by bits of port type select registers PSC. They work in the same way with PULL bit of PMCR but only on single pin, “0” is to disable, while “1” is to enable. VCC PORT DATA REGISTER ( PDR ) PULL-UP PMOS PULL-UP RD_INPUT DATA INPUT PORT CONTROL REGISTER ( PCR ) FIGURE 7-1 Configuration Of Port-A/B/D/E/L Output Mode In case of output function, Write to port data registers Px makes pins to output desired value. This value can also be read back by read instruction. Besides Port-C, the output pins are CMOS type. Port-C have two options of output types: open-drain and CMOS, and is controlled by port type select registers PSC. Clearing bits of registers PSC is for that disable PMOS of output stage and left only NMOS, while setting bits is for CMOS. Port-A is designed for keyboard scan with de-bounce and transition triggered interrupt, while Port-C/D/E are multiplexed with other system functions, and are controlled by PFC, PFD, and PMCR[2:0]. Port-L is shared with LCD specific signals of LCDC. Turning off LCDC by setting LPWR (LCTR[7]) reserves Port-L for GPIO. Selecting respective pins to be GPIO or signals of system function will not affect original settings of I/O directions and types. This entends the flexibility of the usage of function signals. Note: All the properties of pins are still programmable and must be ascertained before they are assigned to system functions, especially the direction of pins. FIGURE 7-2 Configuration Of Port-C |
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