Zakładka z wyszukiwarką danych komponentów |
|
CS82C54-10Z Arkusz danych(PDF) 7 Page - Intersil Corporation |
|
CS82C54-10Z Arkusz danych(HTML) 7 Page - Intersil Corporation |
7 / 22 page 7 82C54 The status register, shown in the figure, when latched, contains the current contents of the Control Word Register and status of the output and null count flag. (See detailed explanation of the Read-Back command.) The actual counter is labeled CE (for Counting Element). It is a 16-bit presettable synchronous down counter. OLM and OLL are two 8-bit latches. OL stands for “Output Latch”; the subscripts M and L for “Most significant byte” and “Least significant byte”, respectively. Both are normally referred to as one unit and called just OL. These latches normally “follow” the CE, but if a suitable Counter Latch Command is sent to the 82C54, the latches “latch” the present count until read by the CPU and then return to “following” the CE. One latch at a time is enabled by the counter’s Control Logic to drive the internal bus. This is how the 16-bit Counter communicates over the 8-bit internal bus. Note that the CE itself cannot be read; whenever you read the count, it is the OL that is being read. Similarly, there are two 8-bit registers called CRM and CRL (for “Count Register”). Both are normally referred to as one unit and called just CR. When a new count is written to the Counter, the count is stored in the CR and later transferred to the CE. The Control Logic allows one register at a time to be loaded from the internal bus. Both bytes are transferred to the CE simultaneously. CRM and CRL are cleared when the Counter is programmed for one byte counts (either most significant byte only or least significant byte only) the other byte will be zero. Note that the CE cannot be written into; whenever a count is written, it is written into the CR. The Control Logic is also shown in the diagram. CLK n, GATE n, and OUT n are all connected to the outside world through the Control Logic. 82C54 System Interface The 82C54 is treated by the system software as an array of peripheral I/O ports; three are counters and the fourth is a control register for MODE programming. Basically, the select inputs A0, A1 connect to the A0, A1 address bus signals of the CPU. The CS can be derived directly from the address bus using a linear select method or it can be connected to the output of a decoder. Operational Description General After power-up, the state of the 82C54 is undefined. The Mode, count value, and output of all Counters are undefined. How each Counter operates is determined when it is programmed. Each Counter must be programmed before it can be used. Unused counters need not be programmed. Programming the 82C54 Counters are programmed by writing a Control Word and then an initial count. All Control Words are written into the Control Word Register, which is selected when A1, A0 = 11. The Control Word specifies which Counter is being programmed. By contrast, initial counts are written into the Counters, not the Control Word Register. The A1, A0 inputs are used to select the Counter to be written into. The format of the initial count is determined by the Control Word used. Write Operations The programming procedure for the 82C54 is very flexible. Only two conventions need to be remembered: 1. For Each Counter, the Control Word must be written before the initial count is written. 2. The initial count must follow the count format specified in the Control Word (least significant byte only, most significant byte only, or least significant byte and then most significant byte). INTERNAL BUS CONTROL LOGIC CONTROL WORD REGISTER STATUS LATCH STATUS REGISTER CLK n GATE n OUT n OLM OLL CE CRM CRL FIGURE 3. COUNTER INTERNAL BLOCK DIAGRAM ADDRESS BUS (16) CONTROL BUS DATA BUS (8) I/OR I/OW WR RD CS A0 A1 A1 A0 8 COUNTER 0 OUT GATE CLK COUNTER 1 COUNTER 2 OUT GATE CLK OUT GATE CLK D0 - D7 82C54 FIGURE 4. COUNTER INTERNAL BLOCK DIAGRAM |
Podobny numer części - CS82C54-10Z |
|
Podobny opis - CS82C54-10Z |
|
|
Link URL |
Polityka prywatności |
ALLDATASHEET.PL |
Czy Alldatasheet okazała się pomocna? [ DONATE ] |
O Alldatasheet | Reklama | Kontakt | Polityka prywatności | Linki | Lista producentów All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |