ISO-CMOS ST-BUS FAMILY MT8920B ST-BUS Parallel Access Circuit Features • • • • • • • • ISSUE 6 High speed parallel access to the serial ST-BUS Parallel bus optimized for 68000 µP (mode 1) Fast dual-port RAM access (mode 2) Access time: 120 nsec Parallel bus controller (mode 3) - no external controller required Flexible interrupt capabilities - two independent/programmable interrupt sources with auto-vectoring Selectable 24 and 32 channel operation Programmable loop-around modes Low power CMOS technology June 1996 Ordering Information MT8920BE 28 Pin Plastic DIP MT8920BC 28 Pin Ceramic DIP MT8920BP 28 Pin Plastic J-Lead MT8920BS 28 Pin SOIC -40°C to 85°C Description The ST-BUS Parallel Access Circuit (STPA) provides a simple interface between Mitel’s ST-BUS and parallel system environments. Applications • • • • • Parallel control/data access to T1/CEPT digital trunk interfaces Digital signal processor interface to ST-BUS Computer to Digital PABX link Voice store and forward systems Interprocessor communications D7-D0 A4-A0 CS DS, OE R/W, WE DTACK, BUSY, DCS IRQ, 24/32 IACK, MS1 Tx0 Dual Port Ram 32 X 8 Parallelto-serial Converter STo0 Rx0 Dual Port Ram 32 X 8 Serial-toParallel Converter STi0 Tx1 Dual Port Ram 32 X 8 Parallelto-Serial Converter STo1 Parallel Port Interface Interrupt Registers Comp/ MUX Control Registers A5, STCH Address Generator MMS VSS F0i C4i VDD Figure 1 - Functional Block Diagram 3-3 3 MT8920B 4 3 2 1 28 27 26 VDD MMS DTACK, BUSY, DCS IRQ, 24/32 STo1 STo0 D7 D6 D5 D4 D3 D2 D1 D0 CS DS, OE R/W, WE A0 A1 A2 A3 5 6 7 8 9 10 11 • 12 13 14 15 16 17 18 28 27 26 25 24 23 22 21 20 19 18 17 16 15 25 24 23 22 21 20 19 IRQ, 24/32 STo1 STo0 D7 D6 D5 D4 A4 A5, STCH VSS D0 D1 D2 D3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 C4i F0i IACK, MS1 STi0 CS DS, OE R/W, WE A0 A1 A2 A3 A4 A5, STCH VSS STi0 IACK, MS1 F0i C4i VDD MMS DTACK, BUSY, DCS CMOS 28 PIN PDIP/CERDIP/SOIC 28 PIN J-LEAD Figure 2 - Pin Connections Pin Description Pin # Name Description‡ 1 C4i 4.096 MHz Clock. The ST-BUS timing clock used to establish bit cell boundaries for the serial bus. 2 F0i Framing Pulse. A low going pulse used to synchronize the STPA to the 2048 kbit/s ST-BUS stream. The first falling edge of C4i subsequent to the falling edge of F0i identifies the start of a frame. 3 IACK Interrupt Acknowledge (Mode 1). This active low input signals that the current bus cycle is an interrupt vector fetch cycle. Upon receiving this acknowledgement, the STPA will output a user-programmed vector number on D0 - D7 indicating the source of the interrupt. MS1 Mode Select 1 (Mode 2,3). This input is used to select the device operating modes. A low applied to this pin will select mode 3 while a high will select mode 2. (Refer to Table 1.) 4 STi0 ST-BUS Input 0. This is the input for the 2048 kbit/s ST-BUS serial data stream. 5 CS Chip Select. This active low input is used to select the STPA for a parallel access . 6 DS Data Strobe (Mode 1). This active low input indicates to the STPA that valid data is on the data bus during a write operation or that the STPA must output valid data on the data bus during a read operation. OE Output Enable (Mode 2). This active low input enables the data bus driver outputs. OE Output Enable (Mode 3). This active low output indicates that the selected device is to be read and that the data bus is available for data transfer. R/W Read/Write (Mode 1,2). This input defines the data bus transfer as a read (R/W = 1) or a write (R/W= 0) cycle. WE Write Enable (Mode 3). This active low output indicates the data on the data bus is to be written into the selected location of an external device. 7 8-12 A0-A4 Address Bus (Mode 1,2). These inputs are used to select the internal registers and two-port memories of the STPA. A0-A4 Address Bus (Mode 3). These address outputs are generated by the STPA and reflect the position in internal RAM where the information will be fetched from or stored in. Addresses generated in this mode are used to access external devices for direct memory transfer. 3-4 CMOS MT8920B Pin Description (continued) Description‡ Pin # Name 13 A5 Address Bit A5 (Mode 1). This input is used to extend the address range of the STPA. A5 selects internal registers when high and Tx/Rx RAM’s when low. A5 Address Bit A5 (Mode 2). This input is used to extend the address range of the STPA. A5 selects Tx0/Rx0 RAM’s when low and Tx1/Rx0 RAM’s when high. STCH Start of Channel (Mode 3). This signal is a low going pulse which indicates the start of an ST-BUS channel. The pulse is four bits wide and begins at the start of each valid channel. 14 15-22 VSS Ground. D0-D7 Bidirectional Data Bus. This bus is used to transfer data to or from the STPA during a write or read operation. 23 STo0 ST-BUS Output 0. This output supplies the output ST-BUS 2048 kbit/s serial data stream from Tx0 two-port RAM. 24 STo1 ST-BUS Output 1. In modes 1 and 2 this output supplies the output ST-BUS 2048 kbit/s serial data stream from Tx1 two-port RAM. In mode 3, information arriving at STi0 is output here with one frame delay. 25 IRQ Interrupt Request (Mode 1). This open drain output, when low, indicates when an interrupt condition has been raised within the STPA. 24/32 24 Channel/32 Channel Select (Mode 2,3). This input is used to select the channel configuration in modes 2 and 3. A low applied to this pin will select a 24 (T1) channel mode while a high will select a 32 (CEPT) channel mode. 26 DTACK Data Transfer Acknowledge (Mode 1). This open drain output is supplied by the STPA to acknowledge the completion of data transfers back to the µP. On a read of the STPA, DTACK low indicates that the STPA has put valid data on the data bus. On a write, DTACK low indicates that the STPA has completed latching the µP’s data from the data bus. BUSY BUSY (Mode 2). This open drain output signals that the controller and the ST-BUS are accessing the same location in the dual-port RAM’s. It is intended to delay the controller access until after the ST-BUS completes its access. 27 DCS Delayed Chip Select (Mode 3). This low going pulse, which is four bit cells long, is active during the last half of a valid channel. This signal is used to daisy-chain together two STPA’s in mode 3 that are accessing devices on the same parallel data bus. MMS Master Mode Select (Reset). This Schmitt trigger input selects between either mode 1 (MMS = 1), or modes 2and 3 (MMS = 0). If MMS is pulsed low in Mode 1 operation the control and interrupt registers will be reset. (Refer to Table 1.) During power-up, the time constant of the reset circuit (see Fig. 8) must be a minimum of five times the rise time of the power supply. 28 VDD Power Supply Input. (+5V). ‡ Pin Descriptions pertain to all modes unless otherwise stated. Mode MMS MS1 Mode of Operation Function 1 1 N/A µP Peripheral Mode The STPA provides parallel-to-serial and serial-to-parallel conversions through a 68000-type interface. Two Tx RAMs and one Rx RAM are available along with full interrupt capability. 32 channel or 24 channel support is available. Control Register 1, bit D5 (RAMCON) = 0 for 32 channel operation and D5 (RAMCON)= 1 for 24 channel operation. 2 0 1 Fast RAM Mode The STPA provides a fast access interface to Tx0, Tx1 and Rx0 RAMs. This mode is intended for full parallel support of 24 channel T1/ESF trunks and 32 channel CEPT trunks. Input 24/32 (pin 25) = 0 for 24 channel operation, input 24/32 (pin 25) = 1 for 32 channel operation. 3 0 0 Bus Controller Mode The STPA will synchronously drive the parallel bus using the address generator and provide all data transfer signals. This mode is intended to support 24 or 32 channel devices in the absence of a parallel bus controller. Input 24/32 (pin 25) = 0 for 24 channel operation, input 24/32 (pin 25) = 1 for 32 channel operation. Table 1. STPA Modes of Operation 3-5 MT8920B CMOS Functional Description control busses are used to communicate between the RAM‘s and a parallel environment. The STPA (ST-BUS Parallel Access) device provides a simple interface between Mitel’s ST-BUS and parallel system environments. The ST-BUS is a synchronous, time division, multiplexed serial bussing scheme with data streams operating at 2048 kbit/s. The ST-BUS is the primary means of access for voice, data and control information to Mitel’s family of digital telecommunications components, including North American and European digital trunk interfaces, ISDN U and S digital line interfaces, filter codecs, rate adapters, etc. The STPA provides several modes of operation optimized according to the type of information being handled. For interfacing parallel data and control information to the ST-BUS, such as signalling and link control for digital trunks, the STPA provides a µP access mode (Mode 1), and looks like a 68000 type peripheral. In this mode, the device provides powerful interrupt features, useful in monitoring digital trunk or line status (i.e., synchronization, alarms, etc.) or for setting up message communication links between microprocessors. To interface high speed data or multi-channel voice/ data to the ST-BUS for switching or transmission, the STPA has a high speed synchronous access mode (Mode 2) and acts like a fast RAM. For voice storage and forward, bulk data transfer, data buffering and other similar applications, the STPA has a controllerless mode (Mode 3) in which it provides address and control signals to the parallel bus This is useful for performing direct transfers to the ST-BUS from external devices such as a RAM buffer. The STPA is a two port device as shown in the functional block diagram in Figure 1. The parallel port provides direct access to three dual port RAM’s, two transmit and one receive. The address, data and µP Peripheral Mode #1 C4i F0i IACK STi0 CS DS R/W A0 A1 A2 A3 A4 A5 VSS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 Two parallel-to-serial converters, and one serial-to-parallel converter interface the dual port RAM’s to the ST-BUS port of the STPA. This port consists of two serial output streams and one serial input stream operating at 2048 kbit/s. This configuration of two outputs and one input was designed to allow a single STPA to form a complete control interface to Mitel’s digital trunk interfaces (MT8976, MT8978 and MT8979) which have two serial input and one serial output control streams. ST-BUS clocking circuitry, address generator and various control and interrupt registers complete the STPA’s functionality. Modes of Operation The three basic modes of operation, µP Peripheral Mode (Mode 1), Fast RAM Mode (Mode 2) and Bus Controller Mode (Mode 3) are selected using two external input pins. These inputs are MMS and MS1 and are decoded as shown in Table 1. Whenever MMS=1 the device resides in Mode 1. In this mode, MS1 pin is unavailable and is used for a different function. When MMS=0, Modes 2 or 3 are selected as determined by input MS1. If MS1=1, Mode 2 is selected and if MS1 =0, Mode 3 is selected. Each of the modes of the STPA provides a different pinout to ease interfacing requirements of different parallel environments. These are shown in Figure 3 below. In µP Peripheral Mode the device uses interface signals consistent with a 68000-type µP bus. Mode 2, Fast RAM Mode, uses signals typical of standard RAM type interfaces. Mode 3 interface signals are very similiar to Mode 2 signals except that the address and control signals are supplied as outputs by the STPA. Fast RAM Mode #2 VDD MMS DTACK IRQ STo1 STo0 D7 D6 D5 D4 D3 D2 D1 D0 C4i F0i MS1 STi0 CS OE R/W A0 A1 A2 A3 A4 A5 VSS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 Bus Controller Mode #3 VDD MMS BUSY 24/32 STo1 STo0 D7 D6 D5 D4 D3 D2 D1 D0 C4i F0i MS1 STi0 CS OE WE A0 A1 A2 A3 A4 STCH VSS Figure 3 - Modes 1, 2, 3 Pin Connections 3-6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 VDD MMS DCS 24/32 STo1 STo0 D7 D6 D5 D4 D3 D2 D1 D0 CMOS 24/32 Channel Operation The STPA may be configured to operate as a 32 channel or 24 channel device. This feature, which is available in all three modes of operation, is particularly useful in applications involving data access to CEPT and T1 digital trunk interfaces. When used as a data interface to Mitel‘s CEPT digital trunks, the STPA maps the 32 consecutive bytes of each dual port memory directly to ST-BUS channels 0-31. This is performed by the address generator shown in the functional block diagram (see Figure 1). Figures 4 c & d show the relationship between relative dual port RAM locations and corresponding ST-BUS channels, for both input and output serial streams, when the STPA is configured as a 32 channel device. When used as a data interface to Mitel’s T1 trunk devices, however, only the first 24 consecutive RAM locations are mapped to 24 of the 32 ST-BUS channels. This mapping follows a specific pattern which corresponds with the data streams used by Mitel‘s T1 products. Instead of a direct correlation (as in 32 channel operation), the 24 consecutive RAM locations are mapped to the ST-BUS with every fourth channel, beginning at channel 0, set to FF16 (ie. channel 0, 4, 8, 12, 16, 20, 24 and 28). Figures 4 a & b show the relationship between RAM locations and ST-BUS channel configuration. This feature allows the STPA to be interfaced directly to Mitel’s T1 trunk family. When the STPA is operated in Mode 1, 24 and 32 channel configurations are selected using bit D5 (RAMCON) in Control Register 1. D5 = 0 selects 32 channel operation and D5 = 1 selects 24 channel operation. When the STPA is operated in Modes 2 or 3, however, the channel configuration is done using input 24/32 (pin 25). When 24/32 = 1 the device uses all 32 channels and when 24/32 = 0 it uses 24. Dual Port RAMS Each of the three serial ST-BUS streams is interfaced to the parallel bus through a 32 byte dual port RAM. This allows parallel bus accesses to be performed asynchronously while accesses at the ST-BUS port are synchronous with ST-BUS clock. As with any dual port RAM interface between two asynchronous systems, the possibility of access contention exists. The STPA minimizes this occurrence by recognizing contention only when accesses are performed at the same time for the same 8-bit cell within the dual port RAM’s. Furthermore, the probability of contention is MT8920B lessened since ST-BUS accesses require only the last half cycle of C4i of every channel. When contention does occur, priority is always given to the ST-BUS access. The STPA indicates this contention situation in a different manner for Modes 1 and 2. In Mode 1, the contention is masked by virtue of the "handshaking" method used to transfer data on this 68000-type interface. Data Strobe (DS) and Data Transfer Acknowledge (DTACK) control the exchange. If contention should occur the device will delay returning DTACK and thus stretch the bus cycle until the µP access can be completed. In Mode 2, if access is attempted during a "contention window" the STPA will supply the BUSY signal to delay the start of the bus cycle. This “contention window” is defined as shown in Figure 16. The window exists during the last cycle of C4i clock in each channel timeslot. Although ST-BUS access is only required during the last half of this clock period, the “contention window“ exists for the entire clock period since a parallel access occurring just prior to an ST-BUS access will not complete before the ST-BUS access begins. Figure 16 further shows four possible situations that may occur when parallel accesses are attempted in and around the “contention window”. Condition 1 indicates that an access occurring prior to the contention window but lasting into the first half of it will complete normally with no contention arbitration. If the access should extend past the first half of the contention window and into the ST-BUS access period, the BUSY signal will be generated. Conditions 3 and 4 show accesses occurring inside the contention window. These accesses will result in BUSY becoming active immediately after the access is initiated and remaining active as shown in Figure 16. Access contention is non-existent in Mode 3 since the parallel bus signals, driven by the STPA, are synchronized to the ST-BUS clocks. Mode 1 - µP Peripheral Mode In Mode 1, the STPA operates as an asynchronous 68000-type microprocessor peripheral. All three dual-port RAMS (Tx0, Tx1, Rx0) are made available and may be configured as 32 or 24 byte RAM’s. Also available are the full complement of control and interrupt registers. The address map for Mode 1 is shown in Table 2. The STPA, in Mode 1, uses signals CS, R/W, DS (Data Strobe), DTACK (Data Acknowledge) IRQ, and IACK (Interrupt Acknowledge) at the parallel interface. The pinout of the device is shown in Figure 3. 3-7 3-8 RELATIVE RAM LOCATION 0 1 1 0 STo0 STo1 1 0 RELATIVE RAM LOCATION 1 0 1 0 1 0 0 X 0 X STi0 RELATIVE RAM LOCATION STo0 STo1 RELATIVE RAM LOCATION STi0 2 2 2 2 1 2 1 2 3 3 3 3 2 3 2 3 3 5 4 6 5 7 8 X 6 9 7 8 9 10 11 12 13 14 15 16 17 18 19 20 3 5 4 6 5 7 8 X 6 9 7 8 9 10 11 12 13 14 15 16 17 18 19 20 5 5 6 6 7 7 8 8 9 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 5 5 6 6 7 7 8 8 9 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 X- unused channels marked X transmit FF16 Figure 4 d) RELATIVE Tx RAM ADDRESS vs. ST-BUS CHANNEL - 32 CHANNEL MODE 4 4 Figure 4 c) RELATIVE Rx RAM ADDRESS vs. ST-BUS CHANNEL - 32 CHANNEL MODE 4 4 21 22 23 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 X X X X X Figure 4 b) RELATIVE Tx RAM ADDRESS vs. ST-BUS CHANNEL - 24 CHANNEL MODE 4 X 21 22 23 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 X X X X X Figure 4 a) RELATIVE Rx RAM ADDRESS vs. ST-BUS CHANNEL - 24 CHANNEL MODE 4 X MT8920B CMOS CMOS ADDRESS BITS MT8920B REGISTERS A6 A5 A4 A3 A2 A1 A0 READ WRITE 0 • • • 0 0 • • • 0 0 • • • 1 0 • • • 1 0 • • • 1 0 • • • 1 0 • • • 1 Rx0 - Channel 0 • • • Rx0 - Channel 31 Tx0 - Channel 0 • • • Tx0 - Channel 31 X 1 0 0 0 0 0 Control Register 1 Control Register 1 X 1 0 0 0 0 1 Control Register 2 Control Register 2 X 1 0 0 0 1 0 Interrupt Vector Register Interrupt Vector Register X 1 0 0 1 0 0 Interrupt Flag Register 1 - X 1 0 0 1 0 1 Interrupt Flag Register 2 - X 1 0 0 1 1 0 Image Register 1 - X 1 0 0 1 1 1 Image Register 2 - X 1 0 1 0 0 0 Interrupt Mask Register 1 Interrupt Mask Register 1 X 1 0 1 0 0 1 Interrupt Mask Register 2 Interrupt Mask Register 2 X 1 0 1 0 1 0 Match Byte Register 1 Match Byte Register 1 X 1 0 1 0 1 1 Match Byte Register 2 Match Byte Register 2 X 1 0 1 1 0 0 Interrupt Channel Address 1 Interrupt Channel Address 1 X 1 0 1 1 0 1 Interrupt Channel Address 2 Interrupt Channel Address 2 1 • • • 1 0 • • • 0 0 • • • 1 0 • • • 1 0 • • • 1 0 • • • 1 0 Rx0 - Channel 0 • • • • • • 1 Rx0 - Channel 31 Table 2. Mode 1 Address Map NOTES: Tx1 - Channel 0 • • • Tx1 - Channel 31 X is don’t care A 6 is bit D4 of Control Register 1 Bit Name Description 7 (Unused) 6 IRQRST 5 RAMCON 4 A6 3 IRQ2MODE Interrupt Source 2 Mode Select. This bit configures the source 2 interrupt generator. D3 = 0 selects “static” interrupt mode; D3 = 1 selects “dynamic” interrupt mode. 2 IRQ1MODE Interrupt Source 1 Mode Select. This bit configures the source 1 interrupt generator. D2 = 0 selects “static” interrupt mode; D2 = 1 selects “dynamic” interrupt mode. 1 IRQ2EN Interrupt Source 2 Enable. IRQ2EN = 1 enables interrupts to occur from source 2. 0 IRQ1EN Interrupt Source 1 Enable. IRQ1EN = 1 enables interrupts to occur from source 1. Table 3. Control Register 1 Bit Definitions Interrupt Reset. This bit, when set high, automatically clears the Interrupt Flag Register and the Interrupt Image Register without these registers being serviced. This bit automatically resets to zero after the register clear is completed. RAM Configuration. This bit configures Tx0, Tx1 and Rx0 RAMS for 32 or 24 byte operation. D5 = 0 for 32 channel; D5 = 1 for 24 channel. Address Bit A6. This bit extends the addressing range for access to Tx1 memory. 3-9 MT8920B CMOS Timing information for data transfers on this interface is shown in Figure 14. The Mode 1 interface is designed to operate directly with a 68000-type asynchronous bus but can easily accommodate most other popular microprocessors as well. Control Registers Two control registers allow control of Mode 1 features. Control Register 1 provides bits to select the type of interrupt, to enable interrupts from two different and independent sources and to reset the interrupt registers. Also contained in Control Register 1 are bits to configure the device for 24 or 32 channel operation and to expand the address range for convenient access to the second transmit RAM Tx1. A description of the bit functions in Control Register 1 is shown in Table 3. Mode 1 provides various loopback paths and output configuration options which are controlled by bits in Control Register 2. Bits D0, D1 of Control Register 2 configure loopbacks using input and output streams STi0, STo0 as described in Table 4. The input stream STi0 can be looped back to source the output stream STo0 as well as receive RAM Rx0. The transmit RAM Tx0 can be looped to source the receive RAM Rx0, as well as STo0 and, the transmit RAM Tx0 can be looped to the receive RAM Rx0 while STi0 sources STo0. The function of these loopback configurations is shown in Figure 5. In a similar way, the output STo1 can be reconfigured for different functionality. Bits D2 and D3 of Control Register 2 allow STo1 to be sourced, with a one frame delay via Tx1 from receive stream STi0. STo1 can also output the result of a comparison of the contents of Tx1 ram with input stream STi0. These output configurations of STo1 are shown in Figure 6 Bit Name 7-4 (Unused) 3-2 CONFIG 1-0 3-10 a and b. Figure 6 c shows the effect of combining these two features. Interrupt Registers Interrupts can be generated in Mode 1 only. Two channels of the ST-BUS input stream, STi0, can be selected to provide an interrupt to the system. Interrupts can be of two types: Static or Dynamic. Static interrupts are caused when data within a selected channel matches a given pattern. Dynamic interrupts occur when bits in a selected channel change state (1 to 0, 0 to 1 or toggle). Interrupts are controlled through two identical paths (1 and 2) consisting of the following registers: Interrupt Channel Address (1/2): The address (0-31) of the channel which will generate the interrupt is stored in this register. Image Register (1/2): The contents of the channel causing the interrupt is stored in this register. Reading this register will clear its contents. Match Byte Register (1/2): In static mode this register is used to store the byte which will be compared with the contents of the selected channel causing the interrupt. In dynamic mode, the bits in this register and the corresponding bit in the Interrupt Mask Register define the type of dynamic interrupt (i.e., 0 to 1, 1 to 0, toggle). (Refer to Table 5.) Description STo1 Output Configuration Bits: D3D2 = 00Normal operation. ST-BUS stream from Tx1 is output on STo1 pin. 01STi0 stream is output on STo1 pin delayed one frame (Figure 6 a). 10STi0 is compared through XOR (exclusive OR) with ST-BUS stream from Tx1 and output at STo1 (Figure 6 b). 11STi0 stream, delayed one frame (via Tx1), is compared (XOR) with the next frame arriving at STi0 and the result output at STo1 (Figure 6 c). LOOPBACK Internal Loopback Configuration Bits: D1D0 = 00Normal operation. No internal loops. 01Loop STi0 to STo0 while still receiving STi0 in Rx0 (Figure 5 a). 10Loop Tx0 output ST-BUS stream to Rx0 input ST-BUS stream while outputting Tx0 output to STo0. STi0 is not received (Figure 5 b). 11Loop Tx0 output ST-BUS stream to Rx0 input ST-BUS stream. Loop STi0 to STo0 (Figure 5 c). Table 4. Control Register 2 Bit Definitions MT8920B CMOS Control Register 2 Bits D3 = 0, D2 = 1 Control Register 2 Bits D1 = 0, D0 = 1 µP STo0 Tx0 STo0 Rx0 STi0 µP Rx0 STi0 Tx1 a) STo1 1 Frame Delay a) Control Register 2 Bits D3 = 1, D2 = 0 Control Register 2 Bits D1 = 1, D0 = 0 Tx0 STo0 µP µP Rx0 Tx0 STo0 Rx0 STi0 STi0 STo1 Tx1 b) b) Control Register 2 Bits D3 = 1, D2 = 1 Control Register 2 Bits D1 = 1, D0 = 1 µP Tx0 STo0 Rx0 STi0 Tx0 STo0 Rx0 STi0 µP STo1 Tx1 c) c) Figure 5 - Loopback Configurations Interrupt Mask Register (1/2): In static mode the contents of this register masks bits in the Match Byte Register that are ’don’t care’ bits 1 - bit masked 0 - bit not masked In dynamic mode, each bit in this register and the corresponding bit in the Match Byte Register define what type of dynamic interrupt is selected. (Refer to Table 5.) 1 Frame Delay Figure 6 - STo1 Configurations Interrupt Vector Register This register shown in Figure 7 is common to both interrupt paths and stores an 8 bit vector number which will be output on the data bus when Interrupt Acknowledge (IACK) is asserted. Bits labelled V2 - V7 are stored by the controlling µP. Bits IRQ1 and IRQ2 are set by the STPA to indicate which path caused the interrupt. This creates unique vectors which are used by the µP to vector to interrupt service routines. This feature may be bypassed by simply not asserting IACK during interrupt acknowledged. Interrupt Flag Register (1/2): In static mode the least significant bit in this register is set to 1 to flag the corresponding path in which the interrupt occurs. In dynamic mode this register sets the bits which reflect the position of the bits in the corresponding Interrupt Register which caused the interrupt. D7 D6 D5 D4 D3 D2 V7 V6 V5 V4 V3 V2 D1 D0 IRQ2 IRQ1 Figure 7 - Interrupt Vector Registers 3-11 MT8920B CMOS Interrupt Modes and Servicing D7 D6 D5 D4 D3 D2 D1 D0 Channel Address Register 1 = Static Interrupt Mode 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 (channel 4 of STi0 selected) A static interrupt is caused when an incoming byte matches a predefined byte. The incoming byte from a selected channel is stored in Interrupt Image Register (1/2) where it is compared with the contents of the corresponding Match Byte Register. The result of the comparison of individual bits is masked by the contents of the Mask Register (1/2) before it is used to generate an IRQ. After a static interrupt occurs, information in the Interrupt Image Register is frozen until the µP performs a read operation on this register. When servicing static interrupts assertion of IACK will cause the contents of the Vector Register, with the IRQ1 or IRQ2 bit set, to be output on the data bus. The service routine can subsequently clear IRQ by reading the Interrupt Image Register. Alternatively, the IRQRST bit in Control Register 1 can be set to clear the associated interrupt registers. Static Interrupts are selected using IRQ1MODE and IRQ2MODE bits in Control Register 1. Interrupts are then enabled to the IRQ pin with IRQ1EN and IRQ2EN bits of the same register. Dynamic Interrupt Mode A dynamic interrupt is generated by a change of state of bits in a selected channel. A 0 to 1 transition or a 1 to 0 transition or a simple change of state from the previous state (toggle) can be detected. The type of transition to be detected is selected using two bits, one from the Match Byte Register (1/2) and one from the Interrupt Mask Register (1/2), in the corresponding bit positions. Table 5 shows how the two registers are programmed. Match Byte Register bit DX Mask Byte Register bit DX Transition Type Detected on Incoming bit DX (x = 0 ....7) 0 0 1 1 0 1 0 1 Mask Bit DX 0 to 1 transition 1 to 0 transition Toggle 0 0 Match Byte Register 1 = Interrupt Mask Register 1 = 0 0 0 0 0 0 (When bit D3 toggles 0 to 1) Dynamic interrupts from interrupt path 1 would then be enabled using the Control Register 1. 0 Control Register 1 = 0 0 0 0 1 As with static interrupts, upon serving a dynamic interrupt, assertion of IACK will cause the contents of the Vector Register, with the appropriate path bit set, to be output on the data bus. The information contained in the channel is frozen in the Interrupt Image Register. To clear a dynamic interrupt, however, the µP must read the Interrupt Flag Register of the path responsible for the interrupt to determine which bit caused the interrupt. The bit in the corresponding position will be set to 1 and reading this register will clear its contents. Alternatively, as with static interrupts, the IRQRST bit in Control Register 1 can be set to clear the Image Interrupt Register, Flag Register and path bits in the Vector Register. Dynamic Interrupts are selected using IRQ1MODE and IRQ2MODE bits in Control Register 1 and are enabled using IRQ1EN and IRQ2EN in the same register. MMS Pin Reset The STPA can be RESET in Mode 1 using the MMS pin (27). Applying a low pulse (0V) to MMS after power is applied to the device will reset all control and interrupt registers to 0016. This can be accomplished on power up with a simple R-C circuit as shown in Figure 8. VDD R STPA MMS 27 C Figure 8 - MMS Reset Function 3-12 1 This would cause interrupt 1 path to be enabled while interrupt 2 path is disabled. Table 5 - Dynamic Interrupt Types For example, the following steps are required to generate an interrupt when bit D3 of channel 4 changes state from 0 to 1 (all other bits are masked): 0 CMOS Mode 2 - Fast RAM Mode MT8920B reads and writes with framing and channel boundary information. Mode 2 operates as a high speed dual port RAM interface to the ST-BUS. Only the two transmit RAM’s, Tx0 and Tx1, and the receive RAM, Rx0 are active in this mode (i.e., control registers and interrupt registers are inactive). The main feature of this mode is fast access to the dual-port RAM’s. Fast access allows high-speed controllers to use this device as a data interface to T1 and CEPT digital links. Timing information is shown in Figure 15. Mode 2 can also support 24 channel and 32 channel operation. The channel configuration is selected using 24/32 pin. When 24/32=0 the device operates in 24 channel mode and when 24/32=1, it operates in 32 channel mode. The physical interface in this mode resembles that of a simple RAM device. The signals used to read and write the device are CS, OE, R/W. The pinout of the STPA in this mode is shown in Figure 3. Address decoding for Tx0, Tx1, Rx0 is shown in Table 6. Contention can arise for access to the dual port RAMS. The occurrence of this is minimized since the ST-BUS serial-to-parallel and parallel-to-serial converters require RAM access for only 1/32 of a channel time (i.e., last half cycle of C4i for each channel). For contention to occur the high speed controller must access the same RAM location as that of the ST-BUS. For a parallel read operation this corresponds to the current ST-BUS channel and for a write operation, the next ST-BUS channel. Access contention in Mode 2 is arbitrated with the BUSY signal. BUSY is intended to hold off any parallel access cycle until it again goes inactive. Figure 16 shows how the access is arbitrated for accesses near the contention window. Applications using high speed access can easily avoid generating BUSY by co-ordinating channel Mode 3 - Parallel Bus Controller In this mode the STPA outputs all necessary signals required to drive devices attached to the parallel port. The STPA can be used to drive devices such as RAM’s, FIFO’s, latches, A/D and D/A converters, and CODECS, directly from the ST-BUS without an intervening µP. As with the other modes, Mode 3 can operate from 32 channels or 24 channels by connecting 24/32 high or low, respectively. This allows devices to be driven remotely via a T1 or CEPT digital trunk link when used with Mitel’s trunk products. Referring to Figure 1, the Address Generator block generates and drives the external address lines A4-A0. The STPA also generates OE (output enable) and WE (write enable) to facilitate data transfers from Rx0 RAM and to Tx0 RAM. Tx1 RAM is unavailable in this mode. The STPA, in Mode 3, generates external addresses in a particular sequence that minimizes throughput delay through the device. When channel N is present on the ST-BUS, the STPA generates address N+1 on the address bus and asserts OE to output data from an external device and latch it into the STPA. During the same channel N, the STPA will generate address N-1 with WE asserted to write from the STPA to an external device. Timing for Mode 3 transfers is shown in Figure 17. All parallel bus signals are synchronized to the ST- BUS clock. The device must be selected using CS in order for the parallel bus drivers to be enabled. CS should remain active for four ST-BUS bit periods (8 x C4i cycles) since a read and a write operation require 2 bit periods each. The STPA generates a signal STCH (start of channel) which becomes active at the start of each channel and remains active for 1/2 of the channel time (Figure 18). This signal may be ADDRESS BITS REGISTERS A5 A4 A3 A2 A1 A0 READ WRITE 0 • • • 0 0 • • • 1 0 • • • 1 0 • • • 1 0 • • • 1 0 • • • 1 Rx0 - Channel 0 • • • Rx0 - Channel 31 Tx0 - Channel 0 • • • Tx0 - Channel 31 1 • • • 1 0 • • • 1 0 • • • 1 0 • • • 1 0 • • • 1 0 • • • 1 Rx0 - Channel 0 • • • Rx0 - Channel 31 Tx1 - Channel 0 • • • Tx1 - Channel 31 Table 6. Mode 2 Address Map 3-13 MT8920B CMOS connected directly appropriately. to CS to enable the device connected on a common bus, to be driven by two ST-BUS streams. Figure 9 shows how this "daisy chaining" of STPA’s is implemented while Figure 10 illustrates the timing on the shared parallel bus. Common Bus OE WE CS STCH Applications STi0 A0 A1 A2 A3 A4 Parallel PBX to Digital Trunk Interface STo0 The STPA is an ideal component for interfacing parallel PBX environments to Mitel’s family of digital trunk devices. MMS MS1 24/32 0 0 CS OE WE 1 Figure 11 shows a typical interface for both T1/ESF and CRC-4 CEPT digital trunks to a system utilizing a parallel bus architecture. Both the MH89760B T1/ESF and the MH89790B CRC-4 CEPT trunk modules are shown interfaced to a parallel bus structure using two STPAs operating in modes 1 and 2. DCS STi0 A0 A1 A2 A3 A4 STo0 MMS MS1 24/32 0 0 1 Figure 9 - "Daisy-chained" STPA’s in 32 Channel Parallel Bus Controller Mode (Mode 3) In order to facilitate efficient use of the parallel bus another signal, similar to STCH, is supplied by the STPA. Delayed Chip Select (DCS) becomes active for the last half of each channel (Figure 19). This may be connected to a second STPA, residing on the same physical parallel bus, enabling it to perform its read/write operations in the second half of each channel. This allows a large number of devices, The first STPA operating in mode 2 (MMS=0, MS1=1, 24/32=0), routes data and/or voice information between the parallel telecom bus and the T1 or CEPT link via DSTi and DSTo. The second STPA, operating in mode 1 (MMS=1) provides access from the signalling and link control bus to the MH89760B or MH89790B status and control channels. All signalling and link functions may be controlled easily through the STPA transmit RAM’s Tx0, Tx1, while status information is read at receive RAM Rx0. In addition, interrupts can be set up to notify the system in case of slips, loss of sync, alarms, violations, etc. CHANNEL N ST-BUS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 C4i Address N+1 N-1 N+1 N-1 OE WE Data Bus IN OUT IN OUT STCH DCS Figure 10 - Timing Relationship for Mode 3 Daisy Chaining 3-14 F0i C4i STi0 STo1 STo0 +5V MMS F0i IACK C4i IRQ STi0 STo1 STo0 † DS R/W DTACK CS A0-A5 D0-D7 (Mode 1) MT8920B +5V MMS MS1 24/32 R/W OE CS A0-A5 D0-D7 +5V†† RxD RxA RxB TxA TxB E8Ko Clock Extractor E1.5i† (E2i††) C1.5i† F0i C2i CSTi1 CSTi0 CSTo DSTi DSTo MT8977/79 MH89760B/790B Rx Line Receiver Tx Line Driver Figure 11 - Typical T1-ESF / CRC-4 CEPT Digital Trunk Configuration NOTES: † Signals applicable to T1-ESF applications using MT8977 and MH89760B †† Signals applicable to CRC-4 CEPT applications using MT8979 and MH89790B * Equalizer MH89761 available for T1/ESF applications SIGNALLING AND LINK CONTROL BUS HIGH SPEED PARALLEL TELECOM BUS (Mode 2) MT8920B C8Kb C4b F0b C2o F0i† C1.5o† MT8940† MH89761* EQU DIP Switch 16.388 MHz Osc. 12.355† MHz Osc. CMOS MT8920B 3-15 MT8920B CMOS Digital Signal Processor to ST-BUS Interface Mode 2 allows many high speed devices to be easily connected to the ST-BUS. Figure 12 shows a TMS32020 digital signal processor interfaced to the ST-BUS through the STPA. This simple interface allows complex functions to be implemented in such systems as PBX’s and computer systems. Some of the possible functions include: - Digital Filtering Voice Conferencing Speech/Data Compression Encryption Tone Detection and Generation Frequency Spectrum Analysis Image Processing µ-Law to A-Law Conversion Echo Cancellation Modulation Speech Synthesis and Recognition 74HCT 138 TMS32020 DS MT8920B E2 A9 A8 E1 A A7 B A6 C CS STo0 A8-A0 A5-A0 STi0 D7-D0 D7-D0 STo1 STRB RW OE WE MSC READY MMS MS1 24/32 +5V +5V Figure 12 - ST-BUS to DSP Interface 3-16 CMOS Connecting the STPA to a shared ST-BUS Line MT8920B a high impedance state at the output of U1, corresponding to the selected channel. The STPA’s STo0 and STo1 outputs cannot be directly forced into a high impedance state. However, with some external logic, the STo0 output can be buffered by a three-state device, controlled by the STo1 output. This application is only possible if the Tx1 RAM and associated STo1 output are not required for some other purpose. Figure 13 shows an external buffer U1 controlled by the STo1 output and an external Output Data Enable (ODE) signal. When FF (hex) is written to the Tx1 RAM, the corresponding STo1 output channel goes to logic high. This signal, AND-ed together with a logic high at ODE, enables U1, resulting in the STo0 signal transparently passed to the output of U1. When 00 (hex) is written to the Tx1 RAM, the STo1 output goes logic low. This disables U1, resulting in This method of three-state buffering permits output control on a per-channel or per-bit basis. The ODE input is used to enable the ST-BUS outputs after all ST-BUS devices are properly configured by software. This eliminates the possibility of contention on the ST-BUS lines during the power-up state. 74HC125 STo0 Parallel Port U1 ST-BUS MT8920B STo1 74HC00 U2 ODE ODE STi0 STi1 STo0 STo1 MT8980 STi7 STo7 Parallel Port Figure 13 - Connecting STPA to a Common ST-BUS Line 3-17 MT8920B CMOS Absolute Maximum Ratings* - Voltages are with respect to ground (VSS) unless otherwise stated. Parameter Symbol Min Max Units VDD -0.3 7.0 V -0.3 VDD + 0.3 V ±25 mA 125 °C 1000 600 mW mW 1 Supply Voltage 2 Voltage on any I/O pin 3 Current on any I/O pin II/O 4 Storage Temperature TST 5 Package Power Dissipation Cerdip Plastic -55 PD PD * Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. Recommended Operating Conditions - Voltages are with respect to ground (VSS) unless otherwise stated. Characteristics Sym Min Typ‡ Max Units 5.0 5.25 V Test Conditions 1 Supply Voltage VDD 4.75 2 Input High Voltage VIH 2.4 VDD V for 400mV noise margin 3 Input Low Voltage VIL 0 0.4 V for 400mV noise margin 4 Operating Temperature TA -40 85 °C 25 5 ‡ Operating Clock Frequency fCK 4.096 MHz Typical figures are at 25°C and are for design aid only: not guaranteed and not subject to production testing. DC Electrical Characteristics - Voltages are with respect to ground (VSS) unless otherwise stated. Characteristics 1 Supply Current Static Dynamic Sym Min ICCS ICCD Typ‡ Max Units 10 5 10 µA mA 2.0 Test Conditions outputs unloaded @fCK = 4.096 MHz 2 Input High Voltage VIH 3 Input Low Voltage VIL 0.8 V 4 Input Leakage Current IZ ±10 µA 5 Input capacitance CIN 10 pF 6 Schmitt trigger input high (MMS) VT+ 7 Schmitt trigger input low (MMS) VT- 8 Schmitt trigger hysteresis (MMS) VH 0.8 1.0 V 9 Output high current (except IRQ) IOH 10 15 mA VOH = 2.4V, VDD = 4.75V 10 Output low current (except IRQ) IOL 5 10 mA VOL = 0.4V, VDD = 4.75V 11 IRQ, DTACK, BUSY Sink Current IOL 10 15 mA VOL = 0.4V, VDD = 4.75V 12 Tristate Leakage A4-A0, OE, WE (mode 3) IOZ ±1 ±10 µA VDD = 5.25V VOUT = VSS to VDD 13 Open drain off-state current IRQ, DTACK, BUSY IOFF ±1 ±20 µA VDD = 5.25V VOUT = VDD 3.8 V 3.0 2.0 VDD=5.25V, VIN=VSS to VDD V 1.0 V 14 Output capacitance CO 15 pF ‡ Typical figures are at 25°C and are for design aid only: not guaranteed and not subject to production testing. 3-18 MT8920B CMOS AC Electrical Characteristics†- Mode 1 Parallel Bus Timing (see Fig. 14) (VCC=5.0V ±5%,TA=-40 to 85°C) Characteristics Sym Min Typ‡ Max Units 1 Address to DS (CS) Low†† tARDS 0 ns 2 R/W to DS (CS) Low†† tRWDS 20 ns tRDS1,2 tcwm tcwm -30 Low†† 3 DS (CS) Low to DTACK tCLK 2*tCLK 4 Valid Data to DTACK Low (Read) tRD 5 DS High to DTACK High tDAR 6 DS High to Data High Imped.(Read) tDHZ 0 7 DS High to CS High tCSH 0 ns 8 Data Hold Time (Write) tDHT 0 ns 9 Input Data Valid after DS tDST 10 Address Hold Time†† Test Conditions ns Load C ns Load A, CL=130pF, RL=740Ω 65 ns Load C, CL=50pF 45 ns Load A, CL=130pF, RL=740Ω tcwm -30 ns tADHT 50 ns † Timing is over recommended temperature & power supply voltages. ‡ Typical figures are at 25°C, VDD=5V, tCLK=244 ns, tCH=tCL=122 ns and are for design aid only: not guaranteed and not subject to production testing. ††The cycle is initiated by the falling edge of CS or DS, whichever occurs last. Timing is relative to the last falling edge which initiates the cycle. (1) tcwm is equal to tCH or tCL whichever is smaller (some ST-BUS compatible transceivers may generate C4 clock having t CHmin=70ns or t CLmin=70ns. (2) Worst case access when memory contention occurs. A0 - A5 tADHT CS (IACK†) tARDS R/W tCSH tRWDS DS tRDS tDAR DTACK tRD tDHZ DATA OUT D0 - D7 tDHT tDST D0 - D7 DATA IN Figure 14 - Mode 1 Parallel Bus Timing † During Interrupt Acknowledge cycle IACK replaces CS. R/W must remain high. 3-19 MT8920B CMOS AC Electrical Characteristics† - Mode 2 Parallel Bus Timing - (see Figures 15 and 16) (VCC=5.0V ±5%,TA=-40 to 85°C) Characteristics Sym Min Typ‡ Max Units Test Conditions 1 OE Low to Valid Data tEVD 60 ns Load A, CL=130pF, RL=740Ω 2 Address Access Time tAA 120 ns Load A, CL=130pF, RL= 740Ω 3 CS Low to Valid Data tCSD 60 ns Load A, CL=130pF, RL=740Ω 4 Output Disable tOHZ 50 ns Load A, CL=130pF, RL=740Ω 5 Address Setup Time tASF 20 ns 6 Data Setup Time tDST 30 ns 7 Data Hold Time tDHT 5 ns 8 Address Hold Time tAH 50 ns 9 Write Pulse Width tWP 50 ns 10 OE, R/W High to C4i High tEC4H -10 ns 11 OE, R/W Low to C4i Low tEC4L 10 ns 12 C4i High to Busy Low tC4BL 50 ns Load C 13 C4i Low to Busy High tC4BH 50 ns Load C 14 OE, R/W High to Busy Low tEBL 40 ns Load C † Timing is over recommended temperature & power supply voltages. ‡ Typical figures are at 25°C, VDD=5V, tCLK=244 ns, tCH=tCL=122 ns and are for design aid only: not guaranteed and not subject to production testing. A0 - A5 tAH CS tASF OE tWP R/W tOHZ tEVD tDST tCSD tAA D0 - D7 DATA OUT Figure 15 - Mode 2 Timing Diagram (No Contention) 3-20 DATA IN tDHT CMOS CHANNEL N - BIT 0 MT8920B CHANNEL (N + 1) - BIT 7 ST-BUS ACCESS CONTENTION WINDOW C4i A0 - A5 READ ADDRESS N or WRITE ADDRESS (N + 1) (N matches incoming ST-BUS channel) CS CONDITION 1: Access begins before contention window and finishes before ST-BUS access - No contention. OE, R/W tEC4H BUSY CONDITION 2: Access begins before contention window and continues into ST-BUS access. tEC4L OE, R/W tC4BL tC4BH BUSY CONDITION 3: OE, R/W Access begins within contention window but before ST-BUS access. tEC4L tC4BH tEBL BUSY CONDITION 4: Access begins during ST-BUS access OE, R/W tEBL tC4BH BUSY Figure 16 - Mode 2 Access Contention Resolution 3-21 MT8920B CMOS AC Electrical Characteristics† - Mode 3 Timing (see Fig.17, 18 and 19) ((VCC=5.0V ±5%,TA=-40 to 85°C) Characteristics Sym Min Typ‡ Max Units Test Conditions 1 CS to OE, WE, Address Enabled tZR 50 ns Load A, CL = 130pF, RL = 740Ω 2 C4i Low to Address Change tACS 110 ns Load A, CL = 130pF, RL = 740Ω 3 CS to OE, WE, Address Disabled tRZ ns Load A, CL = 130pF, RL = 740Ω 4 C4i Low to Output Enable Low tOED 75 ns Load A, CL = 130pF, RL = 740Ω 5 C4i Low to Output Enable High tOEH 75 ns Load A, CL = 130pF, RL = 740Ω 6 OE, WE, Pulse Width tENPW ns Load A, CL = 130pF, RL = 740Ω 7 C4i Low to Write Enable Low tWED 75 ns Load A, CL = 130pF, RL = 740Ω 8 C4i Low to Write Enable High tWEH 75 ns Load A, CL = 130pF, RL = 740Ω 9 Read Data Valid from OE tRST (2*tCLK) -60 ns 50 2*tCLK 10 Read Data Hold Time tRHT 0 ns 11 Write Data Setup Time tWST 70 100 ns Load A, CL = 130pF, RL = 740Ω 12 Write Data Hold Time tWHT 70 100 ns Load A, CL = 130pF, RL = 740Ω 13 C4i Transition to STCH, DCS Trans. tSTC ns Load A, CL = 70pF, RL = 1.22KΩ 120 14 STCH Pulse Width tSCPW 1830 ns Load A, CL = 70pF, RL = 1.22KΩ 15 DCS Pulse Width tCSPW 1830 ns Load A, CL = 70pF, RL = 1.22KΩ † Timing is over recommended temperature & power supply voltages. ‡ Typical figures are at 25°C, VDD=5V,tCLK=244ns, tCH=tCL=122ns and are for design aid only: not guaranteed and not subject to production testing. CHANNEL N BIT 7 (BIT 3) BIT 6 (BIT 2) BIT 5 (BIT 1) BIT 4 (BIT 0) C4i tACS A4 - A0 N+1 N-1 tOEH tOED tENPW OE tWED tWEH tENPW WE tRST tWST tWHT tRHT D7 - D0 DATA IN DATA OUT tRZ tZR CS Figure 17 - Mode 3 Timing Diagram 3-22 CMOS MT8920B CHANNEL N CHANNEL N-1 BIT 0 BIT 7 BIT 6 BIT 5 BIT 4 C4i STCH tSTC tSTC tSCPW Figure 18 - Mode 3 STCH Timing Diagram CHANNEL N BIT 4 BIT 3 BIT 2 BIT 1 CHANNEL N+1 BIT 0 C4i STCH DCS tSTC tSTC tCSPW Figure 19 - Mode 3 DCS Timing Diagram 3-23 MT8920B CMOS AC Electrical Characteristics† - ST-BUS Timing (see Figure 20) (VCC = 5.0V ± 5%, TA = -40 to 85°C) Characteristics Sym Min Typ‡ Max Units 1 Clock C4i Period tCLK 244 ns 2 Clock C4i Period High tCH 70 122 ns 3 Clock C4i Period Low tCL 70 122 ns 4 C4i Rise Time tR 20 ns 5 C4i Fall Time tF 12 ns 6 Frame Pulse Setup Time tFPS 20 ns 7 Frame Pulse Hold Time tFPH 20 ns 8 STo0/1 Delay from C4i tSOD 9 STi0 Setup Time tSTS 100 20 ns Test Conditions Load B ns 35 ns 10 STi0 Hold Time tSTH † Timing is over recommended temperature & power supply voltages. ‡ Typical figures are at 25°C, VDD=5V and are for design aid only: not guaranteed and not subject to production testing. Bit Cell tCL C4i tCLK tFPS tCH tFPH F0i tSOD STo0 STo1 tSTS tSTH STi0 Figure 20 - ST-BUS Timing Diagram 3-24 tR tF MT8920B CMOS 125 µs CHANNEL CHANNEL CHANNEL CHANNEL CHANNEL 31 0 30 31 0 (8/2.048) µs Bit D0 Bit D7 on Data Bus BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 on Data Bus Figure 21 - Format of 2048 kbit/s ST-BUS Streams 2.0 V INPUTS 0.8 V 2.0 V OUTPUTS 0.8 V Figure 22 - Waveform Test Point Reference VDD VDD RL 500Ω CL CL=150pF 6.0k CL=130pF IN4148 LOAD A LOAD B LOAD C Figure 23 - Test Load Circuits 3-25 MT8920B Notes: 3-26 CMOS