参数资料
型号: 73S1209F-68IM/F/P
厂商: Maxim Integrated Products
文件页数: 83/123页
文件大小: 0K
描述: IC SMART CARD READER PROG 68-QFN
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 260
系列: 73S12xx
核心处理器: 80515
芯体尺寸: 8-位
速度: 24MHz
连通性: I²C,智能卡,UART/USART
外围设备: LED,POR,WDT
输入/输出数: 9
程序存储器容量: 32KB(32K x 8)
程序存储器类型: 闪存
RAM 容量: 2K x 8
电压 - 电源 (Vcc/Vdd): 2.7 V ~ 5.5 V
振荡器型: 内部
工作温度: -40°C ~ 85°C
封装/外壳: 68-VFQFN 裸露焊盘
包装: 管件
73S1209F Data Sheet
DS_1209F_004
written into KCOL and KROW registers. The keypad interface uses a 1kHz clock derived from the
12MHz crystal. The clock is enabled by setting bit 6 – KBEN – in the MCLKCtl register (see the Oscillator
and Clock Generation section) to carry out scanning and debouncing. The keypad size can be adjusted
within the KSIZE register.
Normal scanning is performed by hardware when the SCNEN bit is set to 1 in the KSTAT register. Figure
12 shows the flowchart of how the hardware scanning operates. In order to minimize power, scanning
does not occur until a key-press is detected. Once hardware key scanning is enabled, the hardware
drives all column outputs low and waits for a low to be detected on one of the inputs. When a low is
detected on any row, and before key scanning starts, the hardware checks that the low level is still
detected after a debounce time. The debounce time is defined by firmware in the KSCAN register (bits
7:0, DBTIME). Debounce times from 4ms to 256ms in 4ms increments are supported. If a key is not
pressed after the debounce time, the hardware will go back to looking for any input to be low. If a key is
confirmed to be pressed, key scanning begins.
Key scanning asserts one of the 5 drive lines (COL 4:0) low and looks for a low on a sense line indicating
that a key is pressed at the intersection of the drive/sense line in the keypad. After all sense lines have
been checked without a key-press being detected, the next column line is asserted. The time between
checking each sense line is the scan time and is defined by firmware in the KSCAN register (bits 0:1 –
SCTIME). Scan times from 1ms to 4ms are supported. Scanning order does not affect the scan time.
This scanning continues until the entire keypad is scanned. If only one key is pressed, a valid key is
detected. Simultaneous key presses are not considered as valid (If two keys are pressed, no key is
reported to firmware).
Possible scrambling of the column scan order is provided by means of KORDERL and KORDERH
registers that define the order of column scanning. Values in these registers must be updated every time
a new keyboard scan order is desired. It is not possible to change the order of scanning the sense lines.
The column and row intersection for the detected valid key are stored in the KCOL and KROW registers.
When a valid key is detected, an interrupt is generated. Firmware can then read those registers to
determine which key had been pressed. After reading the KCOL and KROW registers, the firmware can
update the KORDERL / KORDERH registers if a new scan order is needed.
When the SCNEN bit is enabled in the KSTAT register, the KCOL and KROW registers are only updated
after a valid key has been identified. The hardware does not wait for the firmware to service the interrupt
in order to proceed with the key scanning process. Once the valid key (or invalid key – e.g. two keys
pressed) is detected, the hardware waits for the key to be released. Once the key is released, the
debounce timer is started. If the key is not still released after the debounce time, the debounce counter
starts again. After a key release, all columns will be driven low as before and the process will repeat
waiting for any key to be pressed.
When the SCNEN bit is disabled, all drive outputs are set to the value in the KCOL register. If firmware
clears the SCNEN bit in the middle of a key scan, the KCOL register contains the last value stored in
there which will then be reflected on the output pins.
A bypass mode is provided so that the firmware can do the key scanning manually (SCNEN bit must be
cleared). In bypass mode, the firmware writes/reads the Column and Row registers to perform the key
scanning.
62
Rev. 1.2
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